the ones i listen to the most are Bourne Identity (all the bourne soundtracks are awesome, but i like the first one the most) Donnie Darko Batman Begins/Dark Knight Blackhawk Down Kingdom of Heaven Event Horizon (this one is SAWEEEEEET) Battlestar Galactica
The Last Samurai has a nice soundtrack for working to. I also like the Gladiator music, and Pirates of the Caribbean. Danny Elfman's original Batman OST is also awesome. I got the OST for The Dark Knight, but I don't really like that very much, it works in the movie but not as working music IMHO.