Solar System

Solar System is - and likely always will be - the most important of the star systems under human control. It contains overwhelming majority of human population, almost the entirety of its industry and - in the post-Blackout era of chaos and everpresent dangers and mind-rending truths - remains the best defended star system of the Known Space.
By all intents and purposes, it's the only place in the Known Space that can be considered a truly safe place from all the horrors that Mankind has encountered ever since they began to explore the Galaxy.

Demographics

Overwhelming majority of the Solar System's population is made up of humans - however, the definition of the word is in the state of constant flux ever since the Blackout. To begin with, there are the Variants - a number of human subspecies created post-Blackout by the rapidly improving human understanding of genetics. Then, there are the transhumans - though only Virtuals ended up properly 'taking off', at least thus far.
And if that wasn't enough, there are also aliens, though thus far only Sidhe showed up clear interest in getting involved with Mankind. However, their genuine attempt to become as human as possible muddles the definition of what humans actually are.

Government

Officially, Solar System is under firm control of the Solar Commonwealth, a pan-national organization created through the Second Treaty of Deimos signed right after Blackout. Practically, though, the situation is much more complicated.
Yes, Solar Commonwealth does exists and is given full, sovereign authority over everything that doesn't belong to any its signatory states. This is the crux of the problem - none of the signatory states are willing to accept Commonwealth's encroachment onto what they're considering to be their 'turf'. It's also actively used to expand said turf, with many pieces of the interstellar cake secured by the Solar Commonwealth being granted to one of its signatories in exchange for its continued existence.
This, however, doesn't mean that Commonwealth's powerless. It has its own army and Navy, full authority over the many survey fleets (that do or do not come back from their expeditions) and has its own judicial system that is commonly accepted to have full authority over cases that transcend borders of its member states. Meaning that while you can't issue an appeal to it from the decision of your country's tribunals, it will be the one to decide the outcome of a feud between - say - two interplanetary shipping companies over some cargo that crossed borders.
The current list of the signatories of the Second Treaty of Deimos:
Mercurial Confederation
Free Republic of Venus
European Sympolity
Visehrad Alliance
Russian Empire
Chinese Federation
East Asian Treaty
North American Trade Union
New Islamic Caliphate
Federative Republic of Brazil
Republic of India
United Lunar Republic
Republic of Mars [membership temporarily suspended]
Iron Pact
Cybernetic Union
Seventeenth Hexagon

Defences

Solar System is considered the best defended star system in the Known Space. And while it doesn't have many competitors on that field, it's still an extremely well-defended star system, whose defences are continously expanded and improved. With the Galaxy beyond its borders being so hostile and dangerous, it truly is only a matter of time before something attacks it after all. And it's better to be ready.
If you exclude the numerous static defenses and planetary armies, the bulk of the Solar System defenses belongs to one of the two organizations:

Solar Defense Fleets

Per the Second Treaty of Deimos, every signatory state is allowed to maintain its own defense fleet (of any size they wish, for as long as they can maintain it) that is composed entirely of non-FTL capable warships, which use the space freed by their lack of Hyperspace Drive to carry heavier weapons and thicker armor. The fact that they aren't expected to operate far away from their ports also allows their fuel tanks to be significantly smaller, freeing even more space.
All those fleets are allowed to operate on their own during peace time, but officialy remain part of the Solar Commonwealth's Navy. They are akin to the US' National Guard of old - if something does threaten the Solar System, they'll be mobilized and tied into the greater strategy to avoid infighting and similar problems. With most local grievances solved and the signatories doing their best to cooperate with each other, fleet exercises between their components of the SDF are pretty common.
Current status of the SDFs is as follows:
Task Group Mercury
Two dreadnoughts, seven monitors and twenty-four corvettes.

Task Group Venus
Four dreadnoughts, twelve monitors and sixty-two corvettes.

Earth's Defense Fleet
European Sympolity Detachment
One dreadnought, seven monitors, twelve corvettes.

Visehrad Alliance Detachment
One dreadnought, twelve monitors, twenty-two corvettes.

Russian Empire Detachment
Two dreadnoughts, eleven monitors, twenty corvettes.

Chinese Federation Detachment
Three dreadnoughts, thirteen monitors, thirty corvettes.

East Asian Treaty Detachment
Two dreadnoughts, twelve monitors, twenty-nine corvettes.

North American Trade Union Detachment
Two dreadnoughts, twenty monitors, forty corvettes.

New Islamic Caliphate Detachment
One dreadnought, seven monitors, twelve corvettes.

Federative Republic of Brazil
One dreadnought, nine monitors, fifteen corvettes.

Republic of India Detachment
Two dreadnoughts, twelve monitors, fifteen corvettes.

United Lunar Republic Detachment
Two dreadnoughts, twelve monitors, twenty corvettes.

Task Group Mars
Three dreadnoughts, twelve monitors, thirty corvettes.

Task Group Jupiter
Two dreadnoughts, fifteen monitors, forty-five corvettes.

Task Force Saturn.
Four monitors, twelve corvettes.

Task Force Uranus
Two monitors, seven corvettes.

Task Group Neptune
One dreadnought, three monitors, twelve corvettes.

Pluto's Defense Fleet
Twelve dreadnoughts, thirty-two monitors and seventy-two corvettes.

This sums up to forty-seven capital ships (twelve of them belonging to Sidhe), one hundred-seventy cruisers (thirty-two of them belonging to Sidhe) and four hundred-seventy nine escort ships (seventy-two of them belonging to Sidhe).

Solar Commonwealth Navy

Solar Commonwealth possesses a Navy of their own (if you exclude Task Force Saturn and Task Force Uranus, both of which are really small and technically counted under Solar Defense Fleets), whose main goal is operating beyond the Solar System.
While most of their ships are outside of the Solar System at any given time, its First Fleet is always there, using its shipyards and other infrastructure to maintain itself while acting as an always ready response fleet to any trouble arising in a neighbouring system. It contains the bulk of Mankind's FTL-capable capital ships.
Right now, the First Fleet is composed of twelve battleships, twenty battlecruisers, twelve heavy cruisers, twenty-seven light cruisers and seventy destroyers.

Industry & Trade

It might appear to be a gross oversimplification of things, but fundamentally speaking, there are four types of goods produced in the Solar System. Each of them is crucial to the continued economic growth, and they are all to some degree intertwined and mutually dependent.

Food

For the first time since Mankind reached for other worlds the issue of food is something that's an actual issue. For now, the only world capable of producing nearly unlimited amount of food is Earth, however its high gravity (even with the usage of orbital elevators due to the high volume of such products) drives the price of such goods up.
In the end, even something as simple as Earth-grown rice or cereals is considered a rare luxury in the Outer System. This is why establishing even indoor hydroponics to produce even the simplest nutrient paste is crucial element of any colonization effort.
Outdoor farms are considered something of a holy grail - especially when they're capable of producing surplus of food that can be exported, and especially when it occurs on a low-gravity world. The more farms you have and the more food you produce, the less dependant you're on Earth.
Today all of the Inner System worlds and the Jupiter System are considered self-sufficient to some degree, although in most cases (again, outside of Earth) the local diet is far from a diverse one and the food prices are much higher than those on Earth.

Consumer Goods

Furniture, clothes, construction materials, electronics, toys and so on. They can be produced in a nearly unlimited amounts, at least for as long as it is made from non-organic materials easy to obtain in space, such as carbon and a variety of metals. Asteroid Belt alone provides nearly unlimited amount of those, with Jupiter Subsystem providing a lot of chemical compounds harvested from Io.
There is no such thing as a shortage of those, with nearly fully automated factories capable of assembling any number of those for as long as the materials are delivered on time. Their prices are fairly low, and they're rarely moved from planet to planet and instead are usually produced on-site from imported resources simply due to not being worth enough to warrant even bulk deliveries.

Luxury Goods

There are goods that either can't be produced anywhere safe for a single place/world and/or are extremely impractical to be produced elsewhere. Here the organic materials dominate, and there is a notable surge of returning to manual labor and older production techniques, both to maintain the scarcity (and keep the price high) and due to the perceived 'fanciness' of such things.
Here, quality and scarcity matter.
Desk made from autentic wood from Earth, handcrafted by a master carpenter. Leather coat from an (ethically sourced) real leather of an animal that an inhabitant of the Outer System can only read about. Numerous beverages that require a particular set of environmental factors to be created. Books printed on authentic letter (if not parchment, which is seeing something of an resurgence). Antiques of any type. And so on.
As can be inferred from the list above, most of the luxury goods today are produced on Earth and exported from there. However, it's only a matter of time before Inner System worlds will join the game.

Industrial Goods

A rather general term for everything required to maintain (and expand) human activity outside of human colonies. Asteroid mining and refining, hydrogen harvesting and turning it into fuel, repairing old starships and producing new ones, Without them, human logistics would collapse, taking the remaining three types of 'goods' with them.
Thankfully, they are usually in excess, if only thanks to the scale of the asteroid mining and the steady expansion of shipyard complexes throughout Sol. The only exception are more esoteric things caused by the recent boom in metaphysics and the 'supernatural' and the new discoveries of the survey fleets of the Commonwealth brought back to the Solar System.

Logistics

It is estimated that at any given time, Solar System is filled with approximately sixty-five thousand civilian spaceships. From this number, about forty-five thousand are freighters of various sizes (from smallest haulers to the largest mass conveyors) while twelve thousands are passenger vessels. The remaining eight thousand are various 'others', including tankers, private space 'yachts', mining vessels and hydrogen harvesters, repair ships and tugs.

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Solar System

Astrography

Mercury Subsystem

Mercury

Venus Subsystem

Venus

Earth Subsystem

Earth
Luna

Mars Subsystem

Mars

Asteroid Belt

Ceres

Jupiter Subsystem

Jupiter
Europa
Callisto
Ganymede
Io
Himalia

Saturn Subsystem

Titan

Uranus Subsystem

Oberon
Titania

Neptune Subsystem

Triton

Pluto Subsystem

Pluto

Local Polities

Human, Commonwealth Members

Mercurial Confederation
Free Republic of Venus
European Sympolity
Visehrad Alliance
Russian Empire
Chinese Federation
East Asian Treaty
North American Trade Union
New Islamic Caliphate
Federative Republic of Brazil
Republic of India
United Lunar Republic
Republic of Mars [Suspended]
Iron Pact
Cybernetic Union

Human, Non-Members

Belt Authority
Free Zone
Elysian Government
Arabian Government

Sidhe, Commonwealth Members

Seventeenth Hexagon