I'm particularly interested in the intersection of computational astrophysics + planetary sciences. Actually, my own institution (Washington) is strong in that since it has Tom Quinn and Rory Barnes, although I'm doing research with another professor right now.
To add to this excellent advice, look for papers on google scholar on stuff you're interested in and track down where the professors are from. Then browse their research web pages and the facilities at that school. The more you show that you've done some of your own homework and can ask more educated and directed questions, the more people are going to want to help you.
I'll try to do more of my own research next time. I actually mostly just wanted a thread for computational astrophysics students to gather around (especially those lurkers who might not have posted already), but I probably should have made that more explicit in the thread title.