Project Euler

Wow - If you are looking for a great web site for exercising you skills in F#, or your programming language of choice, then sign up for ProjectEuler. I've made it through a few of the problems, and they are mind stretchers. I’ve had to try to remember stuff I haven't had to think about for over 15 years! Another advantage of this site is once you solve the problem, you can see how others have solved them in a variety of languages.