Other than Steam (of course) I'll most likely be running the Adobe creative suite (predominantly Photoshop, AfterEffects, and Premiere) and will eventually buy myself a copy of Avid Media Composer 7. I'm a freelance editor and while the vast majority of my work is done in-house with company machines, I figure it'd be a solid investment to get myself a powerful PC so I can do editing in my own time if needs be. I'm also really excited about getting back into AfterEffects as I was a huge fan of the program in ye olde days but haven't had a machine powerful enough to run it properly for some time. Granted there isn't much of a professional use for this right now (I'm currently working for the BBC's natural history unit, which doesn't really call for added explosions and neon motion graphics!) but whatever, AE was always a hobby of mine.
It's worth noting that having a powerful machine when you're a freelancer can also potentially be used to offset the price of the system itself - many production companies in my area either hire kit for editing or hire a suite (which includes kit) at a post-production house, but if you have your own powerful machine and are already being hired as the editor you can offer to provide your own kit for an additional fee. As long as it's up to scratch, your employer saves money because you'll charge a reduced kit rate (compared to a post-house) and you get money for essentially doing nothing.
