Zotero is an open source tool for creating and managing bibliographies. In particular, its greatest strength is the ability to directly add entries you find in the Internet to your bibliography.

Zotero is a plug-in for firefox, it works on Mac OS X, Linux and Windows. There exist plug-ins for open office and MS Word.

You can also use it to manage bibliographies used within Latex.

How to migrate from Endnote

If your bibliography exported to RIS-format, eg. exported from EndNote or ReferenceManager, contains links to files, which cannot be accessed, the import stops at the reference containing this link. This is also true, if these are local paths to files, which are not existing.