John Musser who runs the excellent site Programmable Web maintains a handy list for developers of Application Programming Interfaces (API) grouped by name, date, mashup count and categories like: advertising, answers, blog search, blogging, bookmarks, calendar, chat, community, email, events, fax, financial, internet, mapping, music, widgets and more.

I met John at Search Champs v4 and have been visiting his site since. He’s from the Seattle area too. Keep up the good work, John.