Organize With Nambu
Twitter overload? Don't despair. Nambu speeds through your Twitter friends' updates. It's a free, native app (for OS X only), so it'll run quicker and smoother than Tweetdeck.
I also find it to be much easier to use and navigate, and the UI is classic Mac (look out for the Growl updates of your Twitter followers — something I love but something others may want to turn off!).