Another awesome thing about Flickr is how good its API is. If you look around for web apps and mobile apps that do something interesting with photos, they're a

Another awesome thing about Flickr is how good its API is. If you look around for web apps and mobile apps that do something interesting with photos, they're almost always built using Flickr's API, for good reason: it's likely the most open, easy-to-use, well-designed API for photos out there.