Sentry

Sentry is a little CoffeeScript app built on backbone that lets you preview and cycle through multiple sites side-by-side. To use, pass it a comma-separated list of URLs in the hash.

Demo

http://devth.github.com/sentry/#http://devth.com/,http://github.com,http://jquery.com,http://jashkenas.github.com/coffee-script/,http://nodejs.org