OAuth is an open protocol to allow secure API authorization in a simple and standard method from desktop and web applications.
If you're looking to find out how OAuth really works then this article, How to build an OAuth consumer, is a must read. It walks you through all of the steps involved in being a OAuth consumer with step-by-step examples to follow along with.
The Google OAuth Playground is a great resource for testing out your OAuth queries to see if the problem is with your library or the OAuth details you've got.
- Zend, Twitter, and OAuth Made Easy shows you how to "force" Zend_Service_Twitter to be OAuth aware
Python / Google App Engine
- python-oauth2 just works perfectly.
- Using python-oauth2 to access OAuth protected resources
- oauth.py from tweetengine is nice in that you can easily create new clients. But beware, I had to do a bit of hacking to force it to urlencode the consumer key/secret.