Quizlet is a website that lets you create flashcard type quizzes, and then quizzes you on them. It maintains statistics on what you've answered correctly, and can test you in a variety of ways, such as how many can you get correct in a fixed time,
Requires creating an account, you can create a profile on the site, or use a Google or Facebook account to authenticate.
A basic account is free, letting you create text based quizzes. The site accepts Unicode input. A $15 per year subscription (Quizlet Plus) lets you record audio and upload pictures, a $25 subscription (Quizlet Teacher) allows audio and pictures, lets you create quizzes for your students, and see how they do on them. Subscribing also hides the ads on the site.