I recently ran across this list of Lisp problems and added it to my 'rainy-days' link bin. One afternoon, as I was aimlessly reading posts in the JoS forum (hey, go easy on me; the proxy server at work blocks Google Groups, so I don't have much choice by way of internet entertainment), my conscience piped in that I was slacking off too much, and I decided to assuage it by trying out some of these problems. Once I did a couple of them, my interest in all things Lispy was rekindled.
It's been three days now, and I am at #27. A Lisp hacker will probably cringe at the way I've solved some of the problems, but what the hell, I'm having too much fun to care.