there's quite a bit to do for the community, mostly involving some kind of graphical or music composing work, but also game balancing via the editors available for supremacy and bote and programming in various languages (c++, c#,Blitz3D..) for each game. You'll probably see what's goin on when you stick to the board a little while and who(m) to address to for helping out in certain areas.
I give you a short list of what I think is currently needed:
1. UI graphics (with Gimp, Photoshop, Paint.NET or even a vector graphics program if you know how to handle it, most appreciated IMO, see corresponding "announcement"-threads in the different game subforums). Just help designing a few more bars and design elements for our games.
2. Race emblems. Check the news, there's a thread linked there.
3. 3D ship models. Refer to Kenneth and Trashman for that issue.
4. Minor structure and building pictures. Zeleni's the man for that as well as for 2. (and 3.)
5. Supremacy balancing. Download his package and the botf2 database (latest version), check for the editors and sit together with mstrobel for discussing what you wish to change and adapt for the official release version.
6. BotE balancing. Pretty much the same, only refer to Sir Pustekuchen and Alamar (responsible for the buildings stats list) for that matter.
7. Music compositioning. Talk to EricJames and TerakRall. They sure appreciate more help if you're capable of self-educating yourself in the matter and with the programs.
So I think I covered everything. For further introductions, I think, ppl here will show you the way