A colleague mentioned the existence of Mendeley to me - a new and free reference manager. I've stuck with Papers for a while and was really really happy with it, but I have to admit that Mendeley seems to have quite a few cool features there.

For example: 1) it's free (and hopefully it'll remain like that forever) 2) it provides an online counterpart, so that you can check/manage your reference library online too 3) it's a social application - it aims at building up a community of researchers/users based on the categorization of one of their primary interests: papers 4) it can be used by researchers as a 'research homepage' which features quite a lot about their academic profile..

Conclusion: definitely worth a try!

What else is available in the market?

Not much that handles well both the tasks of a document manager and a social application; however these other tools/apps are worth checking out:

• Zotero: http://www.zotero.org/, "Zotero [zoh-TAIR-oh] is a free, easy-to-use tool to help you collect, organize, cite, and share your research sources. It lives right where you do your work—in the web browser itself."
• Papers: http://www.mekentosj.com/, "Award winning applications for scientific research"
• Citeulike: http://www.citeulike.org/, "citeulike is a free service for managing and discovering scholarly references"
• Qiqqa: http://www.qiqqa.com/, "The essential software for academic and research work"
• Sente: http://www.thirdstreetsoftware.com/site/SenteForMac.html, "Sente 6 for Mac will change the way you think about academic reference management. It will change the way you collect your reference material, the way you organize your library, the way you read papers and take notes, and the way you write up your own research."
• Wizfolio: http://wizfolio.com/, "WizFolio is an online research collaboration tool for knowledge discovery. With WizFolio you can easily manage and share all types of information in a citation ready format including research papers, patents, documents, books, YouTube videos, web snippets and a lot more. "
• Refworks: http://www.refworks.com/, "RefWorks -- an online research management, writing and collaboration tool -- is designed to help researchers easily gather, manage, store and share all types of information, as well as generate citations and bibliographies."

For a more extensive list and analysis, check out this awesome wikipedia page: Comparison_of_reference_management_software