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. There are lots of cat photos, but out of about 50 photos only 5 were true LOLCats complete with catspeak captions.
The other problem with this app is that if you close it down, you have to look at the same cats again -- same photos, same order. It doesn't save your place and it doesn't randomize the pics.
A new release version 1.1 now offers the choice to view photos according to "relevance, interestingness, and newest." Choosing newest will help ensure you don't see the same pics right away... as long as you only use the app every few days. Newest also seemed to show more actual LOLCat photos rather than just cat photos that made someone LOL.
If you want to look at cute kitties, you may enjoy this app, but if you want true LOLCats, then surf over to www.icanlol.com/iphone and get the real thing.