Mendeley LogoMendeley is a freemium reference management software combined with a web-based social network, which belongs to Elsevier. Its strength is the management of pdfs as well as the exchange of resources with other people. Mendeley Desktop is available for Mac, Windows and Linux. For web space extension and private groups a paid upgrade may be necessary.

Reference Manager
Generates citations and bibliographies in Microsoft Word, OpenOffice, and LaTeX.
Read and Annotate
Open PDFs and capture your thoughts through sticky notes and highlights.
Add and Organize
Import and organize PDFs from your computer, EndNote™, Papers or Zotero.
Connect with colleagues and share your papers, notes and annotations.
Backup, Sync and Mobile
Access your papers on the web, iPhone or iPad (Update: App support was discontinued on March 15, 2021).
Network and Discover
Discover papers, people and public groups.