What Tool Will Measure My Impact on Twitter?

Recently my friend, June Dershewitz came to visit me in Portland, Oregon. While we were chatting about work we got on the topic of Twitter and since I spend so much of my time measuring websites, I asked her what tool could I use to measure my impact on Twitter?

Now I am familiar with twitter, but I am not the person who sends tweets that I'm going to the store now or picking up the kids. I also do not sit on Twitter night and day consuming the firehose of information coming through. I want a tool that helps me measure signal, not the volume of noise produced (i.e. number of tweets).

June recommended Klout. And it is really good. Here is why:

Without Registering
1. It's fast. Just enter your Twitter handle and wham! there is data to chew on. Note: there may not be much in there if you are not at least a little active on Twitter.  
2. It's robust. You get three pages of analysis including a very handy matrix that classifies your style of influence, top retweets and most influential topics.

After Registering
1. More charts! The framework stays the same (thank you, good UI people) but now there is an additional layer of detail for the second page on true reach, amplification and network.
2. Dashboard. Don't miss this link at the top which show people you follow and their influence scores as well as topics those top influencers cover. Clicking on the topics will unearth more people you can follow or immitate to move your score up.

What other Twitter measurement tools do you like?