Popular image-sharing application mlkshk now has a mlkshk API for building mlkshk-enabled applications. The service provides a social image discovery and sharing technology, with a RESTful API allowing access to a user's mlkshk account, friends, favorites, and personal image collections also known as "shakes."
While map mashups are what have defined this genre of application, the second most popular type of web mashup here on ProgrammableWeb are photo mashups. How popular? Just this past week the number of photo-related mashups passed the 500 mark, and there are now 505 listed.