I came across the stuff at Exeter who has these problem sets . . . of which most are pretty difficult or at least challenge you to think outside the box a little, which I love.
So, I tried to start a math club (I had a student teacher at the time and was ready to hurt myself b/c I wasn't teaching) which lasted about 3 months, and I looked to use the problem sets.
Been reading some blogs (specifically rationalexpressions.blogspot.com) which brought up the Exeter problem sets in one the posts . . . I think this is something I want to incorporate into my classes. Just need to find a way . . . maybe devote a day - make it a challenge/competition. I need to think about it.
Here's some other things that I'm thinking about:
1. Multiple assessments / recurring topics - I can't test once, say oh you have it in September and not check for retention until December's semester final!!
2. SBG - I love the idea because my job is to make my students stronger mathematically, but even more to appreciate the math, to learn to strive and persevere through the ups/downs of class (uh and life!).