When I quit smoking, learning new things helped keep me from falling back into the old rut. Fresh ideas, fresh hobbies and interests....a really inexpensive hobby for quitters ($100 will get you in the game if you have a computer)
All you need is a camera. take some of the money you've saved from not smoking and get one. you can get a decent one for around $100 and step up after you see if you like it.
here's a few photos I took yesterday afternoon: