My Cat Hates You, a Compendium of Sour-Faced Kitties.

Neatorama reader Kiera suggested this website, MyCatHatesYou.com:

A hilarious group of "sour-faced" kitties with very appropriate captions under each picture. People send in pictures of their pissed-off or just plain mean-looking cats to contend for a spot on the "website of feline doom." Quite amusing.

Link – Thanks Kiera!