As you can see, this is a whole new concept for a dictionary. Words are useless here. You just need to browse it! (Available for English, German, Spanish, French, Dutch, Italian).
A wonderful site with free language resources for almost any world language. It has grammar, it has dictionaries, and in a few words - it has it all. A one-stop site for learners of foreign languages.
A simple and yet VERY useful site for creating tests online for free. I recommend it mainly to teachers that use modern methods of testing - it's a simple and very cool way to encourage students in these technological times. It also provides some sample IQ tests.