There is an excellent article over on Stronglifts about smoking and training.
If you know anyone who both smokes and engages in fitness-improving activities, it's worth forwarding along. Smoking is so counter to all of the work you put in improving your health...yet so hard to quit. The Stronglifts article gives some good reasons to try and recommends a book to help you along. I'm not a smoker, but I've seen many people try to quit...every little bit helps.