It was at one of Scott Crabtree's IGDA Leadership Forum talks that I heard about the book *The How of Happiness* by Sonja Lyubomirsky, and tried it out. It really worked! In the short term, anyway - then I stopped doing the practices in there and returned to my normal borderline-happy self.
So I made a sort-of-a game out of it.
I've been playing the game for a couple of months now and it seems to really work. I'm setting record lows on the CES-D (a clinical measure for depression). By that metric, I almost couldn't be happier.
So, time to share. Maybe it'll work for you too. Be happy.