The free flashcard tool on this site is really useful for teaching English either in - class (if you have a steady internet connection) or to email students a link to your flashcard set(s).
You need to register, but it´s free. And afterwards they system saves your flashcards so you can reuse them at will.
I really like the simple, clean layout of the flashcards, and the intuitive 'quiz' options.
There is an option to set up a timer, and clock the time taken to answer the questions that are randomly generated using your flashcard set, so it works as a classroom race activity ( if your internet connection is fast and reliable).
There is no way to print the flashcards out, or embed them in a website or email, which are major drawbacks in my opinion.
What I like the best is the clean, attractive layout of the flashcards and the incredibly easy and intuitive layout of the flashcard part of the site and quiz options.