Nomee collects many social networks, allowing you to focus on following people instead of websites. It tracks a huge number of social networks. Nomee does not cater to any one social network extensively, including Twitter. Still, it seemed appropriate to write up its actual tweeting abilities for those curious about using this social dashboard.
Nambu is a feature-rich Twitter app for Mac OS X that supports many social networks. It offers plenty of configuration options but has simple defaults for beginners. It also has excellent integration with its sister services, tr.im and pic.im
Twhirl is an Adobe AIR app, so it runs on both Macs and PCs. It can connect to multiple social networks, including Twitter, Friendfeed, identi.ca, or seesmic (who created this software). It receives regular updates and is adding new features with each update. Some of the features include:
From digsby.com:
digsby is a multiprotocol IM client that lets you chat with all your friends on AIM, MSN, Yahoo, ICQ, Google Talk, and Jabber with one simple to manage buddy list. digsby also has a social networking tool that alerts you of events like new messages and gives you a live Newsfeed of what your friends are up to.