Seesmic

Seesmic is an on Adobe Air based Twitter and Facebook client for Mac OS X. Seesmic can manage any Twitter and Facebook accounts, showing the news feed - and Twitter messages in column views well structured. Friends from Facebook and Followers of Twitter can be managed in user-defined groups. Creating answers, private messages and retweets is easily possible via a context menu. When writing status messages, you can choose whether they should be published only on Twitter or Facebook or on both services.