Channel.me offers simultaneous browser sharing, real-time chat, and the ability to add notes and comments right on the page.
Channel.me works much like Google Docs: you can highlight text on a page, add comments and notes to different sections of a web page, and then chat with the other people in your shared browser session.
You can both search the page in real-time, and when one of you clicks a link or navigates forward or back, the other people in the session are notified before the action goes through.
There are even Chrome and Firefox extensions you can install to start a sharing session from any web site without visiting Channel.me first.
Via Robin Good