Google Knol

Google going to launch a Wikipedia like collaberative knowledge repository. They hope that this project will help to record and share knowledge possess by community.
More about Google knol project click Here

CiteULike

CiteULike is a free book marking service to help you to store, organise and share the scholarly papers you are reading. When you see a paper on the web that interests you, you can click one button and have it added to your personal library. CiteULike automatically extracts the citation details, so there's no need to type them in yourself. Users can input a detailed description of scholarly papers. It all works from within your web browser so there's no need to install any software. Because your library is stored on the server, you can access it from any computer with an Internet connection.

http://www.citeulike.org