I recently discovered I CAN HAS CHEEZBURGER? described as
lolcats with tags for your convenience (also for ur lol*s). Yeah. I can't really explain it, except to say it's the funniest blog with cat pictures ever. Also, there's a walrus,.. er, lolrus.
Update (2008-02-23): This has become one of my favorite sites to check daily. I've added their link to the navigation column of this site.