I have been using this English-Chinese dictionary website for a while, and I am really amazed with all the functionalities it provides. Traditionally, if you look up a word in the dictionary, you may forget it in the next day and have to look it up again, and the dict.cn allows you to save all your unfamiliar words into the profile. This is particular useful if you are in a learning process, you can always come back to review the words you have marked before.
Another impressive feature is that the site has collected all the words for a particular subject, say, if you want to review all the GMAT words, you can go there and review that particular subject：
When you review a particular test, you can track all your progress in your profile, this is very cool..