You can submit idioms here: Submit an Idiom - UsingEnglish.com
A wikisite, so people can add definitions anytime
Let people submit more examples for each idiom. Most of the time idioms need the whole context to get a full meaning. Sometimes the meaning of some idiom only gets clear within a paragraph.
I remember the English lecturer telling us the story of the idiom: " It's raining cats and dogs".
The story helped us, as language learners, understand, memorize and use that idiom.
Before I logged in to this forum I was looking for the origin of another mysterious idiom on the net, i.e. "pull up your socks".
Now I wonder why don't native speakers of English take the initiative and ask their fathers, mothers or the elderly ones in their societies to tell us the origins of English idiom to enlighten the learners of English of the historical background of idioms !
If any book, website is available regarding the origins / stories of the idioms, please mention it.