Lately I have writing an API for Micro Site Manager a satellite site generator. This app is currently in Alpha stage and is being tested by a number of my clients.
If written a lot of bespoke PHP code to handle data transfer between the site and the satellite sites. So a Satellite makes a request for page information and this is return with JSON formatted information.
Now I have come across a site were all the hard work has been done for you. This code can generate JSON, XML, CSV and also limit usage per hour per user.
The code on costs $7, so a bargain. I could have coded this myself but this saves me time.