rflickr is a Ruby implementation of the Flickr API. It includes a faithful reproduction of the published API as well as method encapsulation to provide more useful object mappings. rflickr features result caching to improve performance.
Photo editing service Aviary has added a new HTTP-based API that allows developers to pass photos through filters, effects and even basic editing operations. Aviary "soft-launched" the new Aviary Effects API last week at SXSW, when we interviewed Aviary's Michael Galpert (video below). The new service could be used to create photo-sharing services like Instagram, CMS plugins to aid workflow or within social applications to create a standard look to all avatars.
Animetrics, a leading developer of 2D to 3D face recognition and face creation solutions, provides the Animetrics Face Recognition that can be used to detect human faces in pictures and match them against a set of known or documented faces. This tool is specifically useful for applications for the fashion and online entertainment industries, or for law enforcement or military intelligence where accurate identity resolution is a necessity.