Some smart folks out there on the that series of tubes we call the Internet have been putting together interesting projects like this map and this page without any help from us so we thought it was high time to release an API.
Image found at BoingBoing
The Twitter API exposes some of our internal workings using JSON and XML. Note to developers: All of the methods (except for the public timeline) require user authentication via Basic Auth. The username is the email address you have stored on Twitter, the password, your password.