Quizlet is a free application which can help you create flash cards and other studying material for testing. This is available through your computer browser, as well as on Android and iOS mobile devices.
Studyblueis a database filled with study notes in a variety of subject areas. This application does have a free version, with upgrading options for a monthly or yearly fee. Studyblue is available through your browser, as well as on Android and iOS mobile devices.