Maru's blog (the comments under each picture and video are the best)
The trials and travails of Winston and his side kick, Rudy.
Cute Overload! (Repository of all things cute, animal-related)
Junku's Flickr Photostream: Cat Collection
Stuff On My Cat
Cat Prin (English version, but the Japanese version has many more pictures) Cat Prin is a popular online clothing store for cats.