A collection of alllllll the exercises (or at least as many as I could do) from the book/site "How to Design Programs, Second Edition". Content is all available at http://www.ccs.neu.edu/home/matthias/HtDP2e/index.html
As far as I can tell, the exercise solutions are not available at the site. If you're doing the book, maybe this will help. Or, make things worse. ;-)