RandomUser is a new API that returns a JSON object with a randomly generated persona—complete with name, avatar and email address—for your testing purposes. The site suggests using it for design mockups, but the fact that it’s an API opens up plenty of possibilities for more programmatic uses. If you need to fill in a couple dozen users to test an application, you could write a script to populate the database with ones pulled from RandomUser.
The API is neat, but a little limited so far. Hopefully it will be expanded in the future with some additional info.