Seeing things that I don't always see, like Triscuts or Animal Crackers or something. It sounds so stupid, I know. There's also Team America, and the song "Americaaaa FUCK YEAH" Just makes me happy, lol
There's also a lightening storm where I am right now, too. Those also put me in a super-awesome mood.
Totally unrelated question--how many people do you know personally that still use LJ (for anything, whether it be updating journals or commenting in communities)? Other than my sister I seriously feel like the last of my kind, and I only really use it for communities now.