If you twitter - you need Snitter !  Mac / PC no matter. 
The newest version works with both. 

The application runs on Adobe AIR, and you’ll need to download it in order to enjoy all of its features. It very much resembles an instant messaging client. 

To download the latest version (the dev beta kicks the dec 25th verion's ass) go to http://snook.ca/testing/snitter-27.air

ON: Snitter via @jpenabickley