Must see: www.icanhascheezburger.com
Why: It's full of cute pictures of cats and walruses and puppies and things, silly intarweb speak captions, and it's funnier than stuffoncats.com.
Must see: www.xkcd.com
Why: It's an extremely intelligent webcomic that features everything from math to linguistics, and it's delightful.
And Dan recently brought these to my attention 'cause he rules:
Must see: Tiny Animals On Fingers Photoset.
Why: Not only are these adorable baby animals, but it will rock your sense of proportion. Also, the quality of these macroshots is pretty incredible.
Must see: Butterfly Color Palettes
Why: Macro shots of butterflies and corresponding color palettes. It's lovely. I think I want to design a room by using butterfly colors someday.
Just thought I'd share.