Found this interesting article on the 10 best sites created using the Flickr API, it's amazing what people can do.
I'm not a big user of sites like Flickr (in fact the only time i've used it is when New York had the subway strikes and there was loads of interesting pics on there), but some of this stuff is really good.
My favourite is Flickeur
Top 10 FLickr mashups
Moderators: fac51, 117, vinnieza
