Many years back, when I was working in a middle school, I had gotten hooked up with this standardized testing service that needed to employ people like me over the summer to grade stacks of tests from Massachusetts, apparently the standardized testing capital of the country. I wish I could remember the rubric they wanted us to apply; it would make for a great post here. It was alternately a great job - reading all day, comfy chairs, and so on - and a soul-crushing experience (these were high schoolers writing essays, not Charles D'Ambrosio).
One thing I do remember is that every time I found a phrase that had somehow gone through a meat grinder and come out the other end as something poetic and very amusing, I would write it down. I still have the lists of odd phrases somewhere at home. "When the chickens come home to roast" is cited at an article in the New Scientist; apparently, they're called Eggcorns and there's an entire site devoted to them. Linguistics dudes and gals, feast upon it! (via) (here's the RSS feed, if you just want to go straight to delivered linguistic goodness)