Need help with phrase clarification

I would like to find a certain kind of online "phrase" archive -- to periodically use as a reference when writing email messages -- but realized I wasn't exactly sure what search query was most correct.

For example, if I were to comment about the American election by saying that the race was "very close", that would certainly be accurate but it does not convey any emphasis.

But if I said:

"it's as close as a gnat's whisker"

or

"it's as close as white on rice"

then that phrasing strikes me as more descriptive.

Here's another example -- instead of saying "he's not very bright", a person might use "he's as dumb as a fence post".

So what exactly are those kind of phrases? Would they be considered idioms? or colloquialisms? or vernacularisms? or similies? or could they be all of the above?

Thanks for any guidance -- if anyone is aware of a searchable archive where a person could find those sort of phrases, I'd be grateful for the resource address...

[twostep]

I really do not want to step on your toes - some of these terms are rather tied to a geographic area and you may have to explain them before they will have a descriptive impact on your audience.

[Tdol]

http://www.usingenglish.com/links/Id...c_Expressions/

Thanks very much for the resource -- that is as close as I've seen to what I'm hoping to find...

[Red5]

And brand new from UsingEnglish.com...

http://www.usingenglish.com/reference/idioms/

Outstanding!