Many thanks for the kind remark.
I don't know a great deal about other online idiom dictionaries, but we have one here at UsingEnglish.com! See:
http://www.usingenglish.com/reference/idioms/. It's very new and still being developed, but you might be able to find what you're looking for there.
Regards,
Red5
PS - If you have any suggestions for additions to our
idiom dictionary, please feel free to post them in our
Comments & Suggestions forum.