Which sites are worth a few bucks?

[Cadaverous Pallor]

I just visited Wikipedia, and they have a plea for donations up on the site, including a message from their founder. I ended up chipping in a tiny bit because it's one of few sites I truly rely on. I am just as demanding as anyone else that things remain free, but there are sites worth supporting.

Since I know all of you use Wikipedia as much as everyone else, I figure some might be interested in donating over there. I was also wondering if there are other sites you've given to.