A source for interesting / fun problems that aren't necessarily physics problems.
Car Talk Puzzlers. I haven't found a great way to implement them into my class, but they are fun. I am starting to post these questions and the TPT Physics Question of the month for my students as extra credit options. I don't yet feel comfortable requiring a certain number of these problems to be solved in the course of a quarter. I might move in that direction once I have a better feeling for how my students do with them.
< http://www.cartalk.com/content/puzzler/>
Paul Lulai
Physics Teacher
St Anthony Village S.H.
3303 33rd Ave NE
St Anthony Village, MN 55418