Zotero is a free browser tool that keeps track of your articles and webpages, and creates citations in several formats. Sign up for a free account, and your personal library will be accessible from any computer with an internet connection.
In addition to the various citation tools and permanent folders available in many of the Library's subscription databases, there are several free, web-based tools useful for formatting quick citations. Use such tools with caution though: they frequently result in incomplete or incorrect citations. It is ultimately your responsibility to make sure that your citations are correct. Always consult the Library's citation guides as a final step.