Mendeley  is a relatively new online reference manager. It is different to EndNote and Refworks as it also incorporates a social network allowing you to crowdsource papers on your research interests. Mendeley also suggests that it is a useful tool for research collaboration  because you can:
" ... set up a shared library for your team and for specific research projects - your documents, tags, and annotations stay in sync. You can also set up public research paper collections and subscribe to updates. Moreover, Mendeley lets you build your academic profile for others to discover your areas of expertise, and you can create your personal network of research contacts for current and future research collaboration."