Author Scott Thornbury talking about the use of Repetition in English language teaching. For more information see www.macmillanenglish.com/methodology.
Word Stash is a free service that describes itself as "half vocabulary builder, half dictionary, and full awesome." Word Stash is pretty true to its self-description. At its most basic Word Stash is a dictionary that provides contextual examples to support the definitions offered. For many words, Word Stash provides an audio pronunciation.
The vocabulary builder aspect of Word Stash lies in the fact that users can create accounts in which they create and save lists of words to study. Users can create as many lists as they like and expand existing lists as they go. Word Stash provides short quizzes based on the words a user puts into a list. In creating the study quizzes, Word Stash uses a spaced repetition algorithm to present users with words based upon how often they answer correctly or incorrectly. To create a list of words users simply need to click "stash" anytime they view a word in the Word Stash dictionary. Users can also share lists and study other users' shared lists.