My pile of technical paper, journals, white papers, and other information on nanotechnology alone has grown to be unmanageable. This is the advantage of the Internet, several professional memberships, and arVix. I began looking for a reference manager to help with writing a technical paper. Wikipedia has a great summary of reference management tools and I selected three to look at Endnote, Mendeley, and Zotero. Each package has its pros and cons:

• EndNote X4: great integration with MS Word and supports Mathematica (not tested), but has a hard time converting previously stored pdfs to citations. The user interface isn't as good as the others.
• Mendeley: Great at converting pdfs to citations and good at MS word integration. Searching and finding new citations from the desktop applications was not apparent. All citations on the desktop tool get mirrored on your web account on the Mendeley website seamlessly. Sharing is easy perhaps too easy. Great tool and site but worried about information leakage before its time. Mendeley will integrate well with Zotero so that citations from Zotero appear in the Mendeley citation database.
• Zotero: Great integration with Firefox and it's easy to build up a citation database. I wish I used it from the start. It's not so good at converting previously stored pdfs to citations even pdfs from arXiv. This site has online storage and collaboration too, but it lets you can choose to connect to it.

I've had some luck converting my pdfs to citations with Zotero using other openURL resolver sites. Harvard, Stanford, and George Maison University resolver sites have worked fairly well.

Forget about sharing databases and files between the three programs. EndNote would import RIS files from Mendeley. Zotero could not read RIS or Bib files from Mendeley. The EndNote eval program does not export anything useful. There is no one program to rule them all. My ranking

• Zotero for easy of getting citations but needs a better pdf converter.
• Mendeley for great pdf conversion and word integration but wary of the seamless transfer of information to the website that is setup for social networking. This would be my first choice if the connection to the website could be disabled. I would use Zotero to collect citations.
• EndNote for great integration with MS Word but needs better pdf converters.

Also, if you prefer EndNote, it is for sale on Amazon for $187 verses the $250 download price on the EndNote website. The programs are the same but Amazon buys in volume and passes on the discount (according to the Endnote sales rep). Lastly in this information rich world, the citation managers should support all applications not just MS Word. This includes applications like Photoshop, Indesgign, Illustrator, Visio, Wordpress, Tikiwiki, Mathematica, MathCAD, LabView, AutoCAD, SolidWork, and so on.