The main branch of MGTwitterEngine has been updated to support Twitter's OAuth implementation, however it's geared for the iPhone/iPad. With some simple adjustments you can easily use it on the desktop. Instead of using jdg's OAuthConsumer root project, try my fork here, which replaces the custom hmac_sha1 implementation with standard CommonCrypto, which I pulled from roustem's fork.
In a future post I'll do a walkthrough of the basic setup, from cloning the repository, setting up the submodules, and getting a working example.
