StudyBlue

The StudyBlue website is designed to give high school and college students - and teachers - a place to study online. Students can connect with other students, and teachers can set up tools for study such as notes, study guides, and flashcards; pre-made online flashcards can be used or they can create their own, for virtually any subject. Students can take quizzes and bookmark certain items for further study, and homework help is also available with a search engine feature on the website. 

Link: http://www.studyblue.com/