Sorry, I didn't read your post 'til now.
Exercise is a good one. Writing is another for some. I usually try to fix something or create something when I'm like this. Lately, I've been drawing a lot and writing/composing a lot of music. If you're into wood work, that's also a good one and something I did when I had access to shop equipment. Fixing a car, a cabinet and such.
What I'm basically saying is, if you can push yourself to stay somewhat busy and accomplish different things, it naturally uplifts your mood. Also, watching comedies and such are good, too. Humor is a great way of countering depression.