If you recommend goon online English idiom & phrase dictionary.....?

Answer 1

There are some fun individual sites the explore a select set of unusual idioms (often to explain their origins), such as http://www.phrases.org.uk/meanings/index.html.

BUT the ONE place I most count on --advertized as the LARGEST online diom dictionary-- is:
http://idioms.thefreedictionary.com/

You might also try "One Look" which draws from a variety of dictionaries:
http://www.onelook.com/

Answer 2

Here are some good databases for the origin of phrases, cliches, and idioms:

http://www.phrases.org.uk/meanings/
http://idiomsite.com/
http://clichesite.com/alpha_list.asp?which=lett+1