I did a post on my business blog http://thepeoplesresourcesite.wordpress.com about some of the twitter applications that I think are good. Which twitter applications make social networking easier for you?
I really like Tweetdeck as I can see all the conversations with certain search terms. ie I have "Christian" and "affiliate marketing" as two terms and I see everytime someone places a Tweet about those subjects.
I also like Tweet Local as I can see those locally who may want to have info on my local business
I've been using Tweetdeck on my Mac but use http://ping.fm as my Tweet sender for online...easy to use and great tool to pick and choose amongst your social networks to whom you wish certain items sent (Choose to send to LinkedIN, Plaxo, Yahoo 360, Facebook, Twitter, Hotmail Messenger,MSN LIVE, AIM all at once, one at a time or any combo thereof)!
I've been using "Hootsuite" for categorizing and future tweeting, "Twello" is a free yellow-page type of directory for Twitterers, and "WeFollow" is another free listing site all Twitterers are listed on where you can pick 3 words to classify your Twitter account (I'm listed as Christian, Mom, Writer).