Zotero is a reference manager, academic collaboration network and open source developed by an independent, nonprofit organization. Zotero Desktop is available on Mac, Windows and Linux. Zotero Connector functions on all major browsers. Creating an account is free.
Manage references and files on your own computer using the desktop version, then share between computers using the web interface.
Zotero only has the one desktop application, but it can be synced across multiple different devices.
Video courtesy of Carnegie Mellon University.