Immensely helpful - I think Fnord recommended this site:

http://simulator.pokertips.org/simulator.php

I highly recommend running some common scenarios through it so you can get a feel for various odds pre and post flop. I also recommend trying some with multiple hands, even if you just put in random garbage hands, because they will always reduce your winning percentage somewhat. (i.e. if you go all in with AA against AK suited, you're 87% to win... but if you throw in one idiot with 27 offsuit, suddenly you're just 76% to win. And funny enough, 27 guy wins 1% more often than AK guy.)