I keep stumbling into OAuth every day now, in my efforts to learn how it works I've decided to create an OAuth Provider and integrate it into my Zend Framework Application.
Zend Framework doesn't yet (as of v1.12) have an OAuth Provider system in place, though it would be nice!
Here are some links which may be of help:
As I come across better ways to integrate OAuth into Zend Framework I will post them here. If you know of something better than this then please pass on the details.