TweetDeck is a Twitter desktop application based on Adobe AIR which lets you manage your twitter account right from your desktop. TweetDeck is a multi column application through which you can create up to 10 columns and it could also be switch into single column view, it has the ability to catalog tweets, direct messages and replies into different columns.
You can also setup peoples into group to get updates from those group members in a separate column.
Moreover, the best feature I like is that you can continue twittering while you are not connected to internet or when twitter is offline, all the messages queued and sent as soon as you connect to internet or when twitter get back up. You can filter tweets from 1 hour to 48 hours using Timeframe bar.
TweetDeck is really a good functional application for all twitter lovers. TweetDeck is available for Windows, Mac and Linux.