iPhone and iPad apps tagged "LOL cats."
iCaption Harnesses the Power (and Pain) of Community
iCaption (Funny Pics - FAIL Signs, plus more!) is an iphone application for all you Dane Cook fans out there — meaning I don't think it is remotely funny or even tolerable but I guarantee some of you out there will.
LOLCats: Cute, but not always LOL
Cats, yes. LOL, well maybe not so much. The LOLCats app from MC Development brings up photos from flickr with the tag LOLCats. Unfortunately, as with anything that relies on folksonomy, your mileage may vary.