twitchi is perfect for the geek in you... when you want the old school feel of using a command line interface along with access to your social network.
twitchi supports the following features as per the latest release 0.7 (Download) -

• twitchi shortens long urls using bit.ly
• twitchi allows users to read a twitter user's bio, list their friends and followers
• twitchi allows users to search for tweets
• twitchi allows users to add or remove friends
• twitchi allows users to block or unblock users
• twitchi allows users to configure proxy settings for their network
• Provide twitchi access to your account by using a PIN once, and twitchi will remember it for subsequent use
• twitchi allows users to update their Twitter status
• twitchi allows users to view their timeline
• twitchi allows users to send and view direct messages
• OS supported - Windows, Linux

gooey is a light-weight Java Swing based Twitter client, developed on top of twitchi.
As of the initial release 0.1, it supports the following features (Screenshot) -

• gooey allows users to update their Twitter status
• gooey allows users to view their timeline
• gooey allows users to page through their timeline
• gooey allows users to configure proxy settings for their network
• Provide gooey access to your account by using a PIN once, and gooey will remember it for subsequent use
• gooey shows you a count of the number of characters in your tweet, so you don't go over the limit
• OS supported - Windows, Linux

I started this project to learn Twitter integration. I used Twitter4J, since it offers the simplest way of integrating Twitter with java applications.
Since then, I have added on features that I thought were useful.

twitchi is also on Twitter! to keep up to date with latest releases, news and such.

Download it here, and if you like it, let me know.