*EDITED with added content
I've been spending a good amount of time lately resetting my brain with Fallout 3: I have 60 hours logged within the last month. I wanted to share some quick finds that might help people out...
1. If the game crashes or locks up a lot, ramp down the anti-aliasing and filtering settings. I'm running 4x/4x right now, and this is on a quad-core AMD 9550 with Geforce 250 GTS 1GB card in Windows 7. The game is also sensitive to things taking up CPU time: I have to suspend BOINC tasks while playing.
2. After enabling some multi-threading tweak, it seems I can ALT-TAB out of game (at least once or twice). I'll have to have one of the roomies try this with Obilivion.
3. I downloaded Broken Steel with Games for Windows Live, but it hid the data from my game. I found a post on how to manually copy the addon to the game.
3. Great reference site: Fallout 3 Wiki