We manage the Avoice Online digital collection for the Congressional Black Caucus Foundation. They recently asked if the items in their collection could be made to work properly with Zotero being developed at George Mason University. It bills itself as a "next generation" research tool for the humanities and it IS pretty interesting. It allows you to collect bibliographic citations, sites that you want to refer back to, and actual digital resources that you annotate in your own collection. Definitely worth a look if you haven't seen it.

[Zotero's site]