ResearchGate:

ResearchGate creates an opportunity by allowing you to network with the largest global community which is dedicated to science and research. This site helps you to expand your contacts, share your thoughts with others and find potential research partners. ResearchGate profiles lets others know about what you are working on by listing your education and experience, your research interests and sharing publications will help you to make your work visible to your research colleagues all over the world. It keeps you informed on the latest updates in the field of science and technology.

Science Commons.org:

Since the year 2004, this site is focusing on efforts to expand the use of Creative Commons licenses to scientific and technical research.

According to Mary Spiro, Baltimore Science News Examiner, this site is the place to go to find research intended for free sharing, re-using and re-purposing. Science Commons is the site which encourages collaboration so that each researcher is not working in isolation. The aim of it is that the result should be faster solutions, quicker cures and more rapid innovations with the cooperation among scientists.

The common users of this site are Google, Wikipedia, Public Library of Science, Flickr, Al Jazeera.