Wordia is a very interesting "visual dictionary." The site works as a dictionary, with parts of speech & definition, but each word also contains a video of the definition. That's right, you get a user submitted and reviewed video where everyday people simply say or read the definition, act it out, dress up like the definition, etc.
It is a great tool for students just learning the English language, students strengthening their vocabulary, or even as a cool idea for a classroom project. A collegue of mine had her students make videos of important ISTEP Testing Words and Terms. The ISTEP is our statewide standardized annual test in Indiana.
Check out Wordia today, or get out and have your students start creating their own visual dictionaries.