On PHPMaster.com today they're posted the second part of their OAuth series showing you how to use the authentication mechanism to connect to Twitter's API. (Part one is here.

Welcome back to Understanding OAuth - Tweeting from Scratch. This is Part 2 of the two-part series and picks up right where we left off in Part 1 with your returned Access Credentials. Since obtaining the credentials is the grueling part of the process, there's not much more left to do except posting a tweet on the user's behalf. Hopefully you'll find the final steps to be a lot easier to follow and more fun to implement.

They show you how to store the credentials from Part 1 into your session for safe keeping and include a simple form you will use to send a tweet to Twitter. They choose to manually build the HTTP POST request, including the credential headers along with the payload (oauth_consumer_key, oauth_signature, oauth_token, etc).