"PicFog is a real-time Twitter image search engine that’s been around for some time, diligently adding new features, the last of which is support for Twitter image sharing services Twitgoo and Yfrog (it previously only supported Twitpic).
For example, I’ve tried the query “Star Trek” (currently a trending topic) on both PicFog and Google Image Search. Yes, PicFog’s results are messy, with lots of user-generated images that don’t have much to do with Star Trek, but all of the results that are relevant are tied to the new Star Trek movie (which, by the way, I can warmly recommend, even for non-trekkies) – images of actors from the movie, photos from screenings, posters and so on. Google, on the other hand, returns a bunch of old Star Trek images. Yes, these are nice images, but none of the results on the first couple of pages have anything to do with the new Star Trek movie.
Let’s try something else; for example, a gadget that’s been around for some time, but has only recently been officially announced – Palm Pre. Google Image Search definitely returns nicer images, but once again,PicFog’s results are much more relevant to the current developments around Pre – you can find screenshots of Sprint’s Pre ad campaign, unveiled yesterday, Pre’s official price list etc."
(http://mashable.com/2009/05/20/picfog/)