Noodle Tools - This powerful tool allows students to take notes, create citations, and produce reference pages. There are additional resources for teachers. Students have to sign up, but it's free
BibMe - The fully automatic bibliography maker that auto-fills. It's the easiest way to build a works cited page. And it's free.
Citation Machine - helps students and researchers to properly credit the information that they use. Its primary goal is to make it so easy for student researchers to cite their information sources, that there is virtually no reason not to.