Online diagramming service Creately opened its Creately API to the public this month, and with some surprisingly innovative features. While providing obvious features to make its service available to outside developers, and several "above and beyond" features, such as easy embedding of diagrams, Creately has done something fairly unique: open up its own, web-based file format for other developers to use.
Seevl is a new kind of music discovery engine. It allows you to find how artists are similar to each other and which artists are most similar to each other, among other things. It also allows you to comment on the notes about artists within the database. This is all well and good, but better yet, it has the Seevl API, allowing developers to integrate Seevi into their own applications.