Attentionmeter is a good idea. According to Steve Rubel:

"…a neat web application that triangulates traffic graphs from Alexa, Compete, and Quantcast. It's called the Attentionmeter. I am not sure about the name but I can live with it. Even better, there's a handy dandy bookmarklet (yum, I love bookmarklets) so you can track any website you're browsing. Just drag this to your faves. Thanks to Jay Meattle for slipping that one to me via del.icio.us."

Improvements - I'd like to see a lot more data pulled in from Alexa - the new "international" information, and Quantcast's keyword and site stats information.  Would not mind some Microsoft AdLabs data thrown in the mix.