Hi Eddie, I have the links to these ones.  I could say that dictionaries tools for the hobby of learning English.   However, I sometimes have to found a word or expression and the regular ones don´t deliver, believe me; there some tricky definitions like "zip gun"    and others that don´t appear usually in the dictionaries.     So, I would add  to the list:

http://dictionary.reference.com/

http://www.websters-online-dictionary.org/

http://www.onelook.com/

http://www.dictionary.net/

http://www.thefreedictionary.com/

http://oxforddictionaries.com/

http://www.urbandictionary.com/

     Other trick I do is to put the term(s) into Google and type "definition", all dictionaries with that definitions or description will appear.