Mendeley is a PDF and citation manager that indexes and organizes your research library into a digital bibliography. The program includes a collaboration component that allows you to share citations with other researchers. Mendeley is both a desktop application and a web-based application.  

To begin, click the "join this group" button on the Stanford Mendeley Group page. The Stanford Mendeley Group account offers students, faculty, staff and researchers 25 GB of storage and the ability to create unlimited private groups with up to 25 users per group.

Documentation and tutorials: