Some of the new additions to the TweetDeck landscape:
1) The online TweetDeck (Beta) Directory makes it easy to find people you may want to follow by category going beyond the limited (and somewhat controversial) 'SUL' (or Suggested User List) and .... the directory's individual categories can be added to your Tweetdeck client with one click from the web. (Kinda cool :)
2) The new version of TweetDeck adds support for MySpace.
There are other changes including drag and drop for links and photos and improved support for Facebook. The complete list can be found at the company blog here.
You can download the latest (free) version of TweetDeck here.