Well, I tried the "blank out the correct answer on a multiple choice question" idea. None of us liked it. I asked for feedback from the kids after they worked on 5 problems, and they said, "well, it's okay if you get one of the wrong answers, but if you don't, then you don't know if you're not doing something ELSE wrong or if you're correct." I think I agree with them.
I went to "math camp" today (calculus teachers sharing materials), and I have a new appreciation for Winplot. It's a free software you can download from Exeter acadamy, and I've only used it for creating graphs for handouts in the past. BUT. One of the teachers showed how he used it for demonstrations in class and such. I'm by no means even close to being an expert, but it gave me motivation to learn more skills in the program. Apparently, they also have WinGeom, and WinStat ... or something like that. I haven't looked into it.