暖簾に腕押し
noren ni udeoshi
not worth doing
waste of effort
才色兼備
saishokukenbi
being gifted with both intelligence and beauty
白昼堂々
hakuchūdōdō
openly (unashamedly) in broad daylight
虎視眈々
koshitantan
vigilantly with an opportunity to prey upon
with an eagle eye
Is there a site or list or something where one can find expressions like these?
Also roughly how many are of these kind of expressions?
Except the first, those words are called 四字熟語{よじじゅくご}. Some of those originate from Chinese idioms. Others are simple compositions of two usually 2-character words. Since their origin is mostly Chinese, they are usually read as Onyomi (that's why the first word doesn't fall in this category).
There exist several online dictionaries for these 四字熟語, e.g. on http://yoji.jitenon.jp/cat/yomi11.html I was able to find 才色兼備. The sheer amount suggests however to not learn them all like a simple vocabulary list. I'd suggest to learn them after witnessing native speakers using them.
http://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q1279540217
四字熟語は全部で何個ぐらいあるんでしょうか？
私の持っている四字熟語の辞書には、 ４０００語載っています。 漢字検定協会で発行しているものです。
I thought 暖簾に腕押し was part of Iroha karuta, but i was wrong.
Iroha karuta includes “とうふにかすがい” and 「ぬかに釘」 which mean the same thing.
http://iso-labo.com/labo/iroha.html
の 喉元過ぎれば熱さを忘れる 鑿（のみ）と言えば槌（つち） 野良の節句働き
