Update:

The Readability bookmarking service will shut down on September 30, 2016

Readability is a tool that makes reading online much easier. Very often, web pages are cluttered with lots of sidebars, ads and additional content that make online articles more difficult to read. Readability, created by Arc90 Labs, removes the surrounding material, leaving the main article much cleaner and easier to read. Readability works with most browsers and is easy to install on your computer or mobile device.

Watch this video to see how it works.