Alexa Toolbar

The Alexa Toolbar, an Alexa Internet product, is a web browser toolbar often used to measure website statistics. It includes a popup blocker, a search engine, a link to Amazon, a link to Alexa, information about the current Alexa ranking of the website that you're visiting, and links relevant to the site you're browsing. The toolbar is only compatible with Internet Explorer on Microsoft Windows.

There are some privacy fears with this toolbar, as the toolbar sends browsing habits back to Alexa.