I think everyone's a little different in terms of what works for them... but what I do (when I can work up the motivation) is to pick up something new. learn a new language, skill, take up a new hobby.... something like that. I really enjoy learning new stuff, and it makes me feel productive. that usually gets me out of my rut. For instance, I've just taken up bikram yoga. i'm getting a workout, increasing my flexibility, and pulling myself out of a particularly low time of my life. 🙂 I just figure there are a ton of things i've 'always wanted to do', and checking them off the list (or even just going through the planning stages) really peps me up... and if I get myself focused on something other than myself, i feel much much better.
also... i normally don't cry at movies, but when i'm really depressed, sad movies can be really cathartic. you'd think they'd make me sadder, but i think they help me to vent. 🙂 I don't even remember what I was watching last night, but I sure cried a lot, and I felt MUCH better afterwards.
though again, everyone's different. Also, most schools have counsellors who you can talk to about your depression for free. In any case, good luck with it all ... Hang in there and you'll make it through. 🙂