I'm always interested in more raw materials. I realise it'd be a lot of work revamping the already confusing economy but having more basic resources and more complex industry chains would be quite a nice achievement. There's too may of them to explain each one in detail, though.
Raw materials could include things like:
Iron Ore
Coal
Bauxite
Oil
Lumber
Pulpwood
Silicon
Sand
Uranium
Energy Cells (Batteries)
And then add the industries which refine these materials:
Steel Mills/Foundries - Turn Ore and Coal into Steel (one would imagine that steel would maintain its' prelevance in construction that is has today)
Aluminium Mill - Turn Bauxite into Aluminium (as per steel, I don't see it disappearing).
Oil Refineries - not everything will be powered by fusion will it?
Lumber Mills, Paper Factories - not every planet has its' own lumber supply.
Glass Factories - The need for glass, too, isn't going anywhere.
Nuclear Facilities - Some of the largest stations and bases would need to produce their own power.
Solar Power Plants - Not every station can produce its own power, that's where these SPP's come in. Like Oxygen or water, energy cells are cheap and plentiful and should be low-value, low distance, perhaps as a loot item.
For most of the above their respective buy and sell points would explain themselves, ie; steel sells from a foundry such as Pueblo and is bought at places where steel would be in demand (generally places with a lot of active construction), increasing in price as the distance from the production site increases.
Yeah, I've been playing too many *-Tycoon games.:$