What do you like in terms of instruments and mood? That dictates what I recommend, but here's what I typically listen to:
Wagner, Chopin, Bach, Ravel, Stravinsky, Mahler, Shumann.
The moody, heavy stuff does it for me; piccolo or flute solo numbers have me wanting to ram the instrument down the player's throat, so most of the classical stuff I prowl through is heavy on horns, cello, violin...
...instruments with depth to them.
Anyway, my typical warning is that if you are on anti-depressants, most of the above composers are NOT for you. Some of Mahler's and Wagner's movements in and of themselves make you want to run for a bottle of scotch and a pack of razor-blades...
It's great stuff, but in small doses. The best thing is to mix it up with lighter compositions; too much Vivaldi has me wanting to retch where too much Mahler will put one in a terrible melancholy.
