Quick plug for Connotea.

[sensaes]

"Saving references in Connotea is quick and easy. You do it by saving a link to a web page for the reference, whether that be the PubMed entry, the publisher's PDF, or even an Amazon product page for a book. Connotea will, wherever possible, recognise the reference and automatically add in the bibliographic information for you. In Connotea you assign keywords (or 'tags') to your references. These can be anything you like, and you can use as many as you like, so there's no more need to navigate complicated hierarchies of folders and categories. Connotea shows you all the tags you've ever used, so it's easy to get back to a reference once you've saved it."

http://www.connotea.org

(Cheers to J.)