Enter Plurk; it's another Twitter clone which takes the Twitter concept and puts it on a timeline. The service has an odd, quirky feel to it; it's much more visual than Twitter, and it's fun to use. It uses colors to emphasize your 'moods', and it introduces the concept of karma, which should be familiar to Reddit users; the more you use the service, the more karma you get. In this case, karma even lets you unlock certain features, which almost feels like a mini game (if you like very boring mini games). Finally, just like Pownce, Plurk lets you divide your friends into "cliques", which is just a fancy word for groups.
twhirl is a social software desktop client, based on the Adobe AIR platform.
Some of twhirl's features:
* runs on both Windows (2000/XP/Vista) and Mac OSX
* connects to multiple Twitter, laconi.ca, Friendfeed and seesmic accounts
* notifications on new messages
* shorten long URLs (using snurl, twurl or is.gd)
* cross-post twitter updates to Pownce and Jaiku
* post images to TwitPic
* search tweets using Twitter Search and TweetScan
* timeline filtering
* color schemes
* automatically check for new versions
There are a lot more things twhirl can do to improve your twitter experience, and it offers various configuration options to adapt to your personal needs.