You could do what I usually do when I'm feeling down and go get sucked into some pointless extended flamewar on Usenet. I don't think I'll know how to emotionally self-destruct properly any more once I stop reading news.groups.

(For more serious advice, I would second the reading thing, since that's what I love doing when I'm alone, but I thrive on being alone and would be taking this as an opportunity to have time to myself, thus indicating that you and I have rather different personalities and my advice probably wouldn't work for you. Which means that what you probably should do is go find some friends, go out to dinner, and find something to do with yourself after work that involves being around people.)