lingro is a free multilingual AJAX dictionary and language learning site. Currently supporting English (ESL), Spanish, Italian, French, and German.

lingro’s mission is to create an on-line environment that allows anyone learning a language to quickly look up and learn the vocabulary most important to them. Whenever we’re developing new tools for lingro or planning the next big step, there are two principles we always consider:

• Knowledge and information essential to human communication and interaction should be free and accessible to everyone. This is why we created the most comprehensive set of free dictionaries available under open licenses so that anyone can contribute, download, redistribute, and modify the dictionaries for their own needs. These licenses guarantee that they will always remain free and useful to society.
• To have the best dictionaries, you need to have the best tools. Every tool we create, from games, quizzes, and study tools to in-context word lookup is designed for you, the user. To us, this means that they should be intuitive, fast, easy to use, and hopefully fun. :-)