Three sites I go to when I need cheering up;
The Nth Degree is a US-based disability culture website with attitude. My favourite area is the Catalogue which includes some great humourous T-shirts for crips.
Subversive Crossstitch (contains strong language) I found completely by accident but totally love it and the story behind it. Ever since I have been a duffer, folks have tried to get me into cross-stitch but have so far failed. Maybe I need one of these kits.
Engrish.com I consider the funniest site on the web. It is full of mistranslations from Japanese to English on packaging, signs, clothing etc. I don't know why linguistic mistakes crack me up so, but they do. I can look at these pictures for hours with tears running down my face, but from experience I know that a lot of people don't really get the joke.
Then a lot of people wouldn't see anything funny in the fact that Powergen's Italian website was originally www.powergenitalia.com - I guess I've just got arrested development of the funny bone or something.