Doing a search will give you untold bounds of information, this thread is going on right now in the tying forum:
http://www.paflyfish.com/modules/newbb/viewtopic.php?topic_id=16363&forum=5
You can start with any cheap thing, it'll work. Some guys still use the most basic. Or, you can get by with a low cost, no frills rotary (ie, griffin odyessy or danvise), or you can spend spend spend (regal, peak, and renzetti seem to come up the most).
Pick a price range and go crazy.
Flyfishohio.com had a good breakdown of low cost vises, too.
http://www.flyfishohio.com/Vise%20Review%201/Fly_Tying_Vise_Shoot-Out.htm