retweetrank
Retweetrank does exactly what the name suggests. It tells you your ranking in the Twitter ecosystem based on the number of times your Tweets are retweeted by others!
The image below is a screen shot which shows you my rank. A lousy 1150 currently.

Traffic rankings are sourced from multiple sources, if available, for the Twitter application. This includes Alexa, and Compete rankings.
March 14th, 2009 at 10:50 PM
This app is great to show who gets reweeted. But it’s somewhat buggy, and doesn’t seem to work correctly all the time. My “rank” hasn’t changed and I’ve gotten many more retweets. I’m not sure if I believe the statistics. And sometimes the tweets will just blank and you get a rank of 0.