The most popular amongst the nicotine replacement products is nicotine gum, and Nicorette is the most popular brand name, though most (if not all) nicotine gums are about the same, though the generic packaging is a little less sexy. Nicorette does have the added advantage of offering several different flavors, none of which taste particularly good. I mean, you're not going to get Hubba Bubba here, but the Mint and new "Fruit Chill" flavors aren't particularly disgusting.
The way nicotine gum works, as you'd expect, is that it delivers low levels of nicotine into your system, and if you do it right, you can keep the flow running for most of the day, which does tend to curb cravings and it helps, to some degree, with the oral fixation issue many cigarette smokers have. An unintentional, though beneficial, side effect to nicotine gum is that, for those of you who slip, you may find that cigarettes don't give you near the same pleasure after chewing on a wad of nicotine gum -- the gum doesn't necessarily block the nicotine from cigarettes from coming into your bloodstream, but it does certainly feel like it.
The nicotine gum literature usually suggest that, if you're a person who waits at least half an hour after waking up in that morning, that you should go with the 2mg gum, and if you have to puff away before you've even left your bed, that the 4 mg gum is more ideal. I'm not entirely sure why they've come up with this distinction, but I might suggest that heavy smokers, or even moderately heavy smokers might want to go straight to the 4 mg gum, because it does offer you a better chance at avoiding the relapse. Until you've really gotten comfortable with not smoking, I wouldn't recommend bumping it down to the 2mg level, though the packaging does offer some helpful guidelines, which even suggest that you start out with around 10-12 pieces a day, which -- even for a heavy smoker -- may feel like overkill. Basically, I recommend having a piece whenever you feel the craving coming on, and don't wait until it's already hit you, cause then you'll be jonesing for a Marlboro.
There are some disadvantages to the gum, however. One, for folks looking for something to do with your hands, it doesn't offer a lot of reprieve. Second, well, it doesn't taste particularly good, especially after the flavor has disappeared, which generally only takes around 10 minutes, but you may find yourself chomping on it for another hour. You're also advised to chew it a little, and then plant it in between your gums and your cheek, where the nicotine has a place to enter the bloodstream. I'd advise doing as much, but I would warn that -- in my experience, at least -- I have run into problems with canker sores after chewing the gum for an extended period of time.
Overall, however, I'd give the nicotine gum a solid B in terms of effectiveness. It certainly goes a long way towards curbing the cravings, but you sometimes don't look particularly flattering when you have a piece of chewed gum stuck between your top lip and your gums, which isn't so great for board meetings and the like.