Somethign that is totally non-chemical that I found very helpful... take the pen cap, like a just a standard Bic pen cap is perfect (but anything with a few small holes should work fine.) Then as frequently as you'd like take in a very LONG sustained breath through the cap, hold it for a little bit and breathe out without the cap... you don't need to try to breathe out slow at all.

Part of the relaxing aspect of smoking cigarettes, is the controlled breathing you perform while smoking, and this simply simulates that... it was essential for me when I quit 8 years ago, and I still find the practice extremely relaxing. GL