The CiteULike site is a free service designed to help individuals manage and discover scholarly references. Sponsored by the Springer group, the service allows users to click on a paper they find online, and it will be automatically stored in their personal library. The service is "social" in a matter of speaking, as visitors can share this library of references and papers with others. CiteULike also has a flexible filing system based on tags, and visitors can customize these tags as they see fit. It's a fantastic resource, and it's compatible with all operating systems.