Oxford university publication is well known name in the publishing world and its dictionaries are simply those you can rely
on easily for perfect meaning of words. Here I am talking about Oxford Advance learners English to English dictionary.
If you are not from english speaking lot and you are learning english than this dictionary is for you. I am personally using the hardcopy from one and the half years and now I am using its online dicaionary which is very helpful.
The good feature of dictionary is that meanings are given for non English speaking world and they are explained as if they are explaining to a child not knowing how to speak, that takes a lot of effort and that makes the dictionary easy to understand even if its a very basic word which we can not simply explain to someone. Else than the dictionary this site is some fun for english learners their are some links well classified according to your level of English to play games, puzzles learn vocabulary and test your skills of vocabulary. There is also a newreader section where you can find news and there is also something for english teaching related to books and all that stuff. There is also grammer learinig section if you want to learn grammer.
I think this site is very helpful for new english learners.