Finding Commonly Used Chengyu Online

I’ve scouted a few places, but haven’t had much success in separating the useless chengyu from the useful ones.

Even when I use the MOE’s concised dictionary, my girlfriend tells me that some of the chengyu that I know use different Hanzi more often, or that they’re outdated (so even if you know them, people aren’t likely to use them in any situation).

Is there a site or publication which has taken the guesswork out of that?

Also, there are some four-character strings that are commonly used and resemble chengyu, but don’t seem to be counted as chengyu (e.g. 一言一行, [yi1 yan2 yi1 xing2], 不乾不淨,吃了沒病 [bu4 gan1 bu4 jing1, chi1 le5 mei2 bing4], 岌岌可危 [ji2 ji2 ke3 wei1]).