Zotero is a great research tool for students and academics. I find it immensely easier and more intuitive to use than EndNote, RefWorks, and other sorts of similar packages. If by chance you’ve been missing out on all the fun, you can get a quick overview here. Their latest and greatest effort is a standalone version that would work with browsers beyond the ever-extensible Firefox.
One thing Zotero makes easy to do is sharing. It’s drop-dead easy to create groups ( essentially, click the group folder icon and send email invitations). One thing I’ve noticed with Group libraries though is the lack of a search function within a specific group’s bibliographic library. This isn’t a big deal if the group doesn’t have a lot of cites that they’re sharing, but if there are a bunch of cites being stored there (e.g., more than 50), searching for them becomes a little unwieldy because you’re going to have manually click through multiple screens. I don’t know how widely the Groups feature is used among the Zotero community, but if it’s a feature under consideration, I’d vote for it in a heartbeat.