Smokefree.gov 
This site from the National Cancer Institute provides free information and professional help to people trying to quit smoking.

Smokefree Women (for Women)
This website combines content available on smokefree.gov with additional content and resources especially for women.

Become an Ex 
This site helps you "re-learn your life without cigarettes," and helps you develop a free personalized quit plan.
This site is also available in Spanish.

QuitNet
This site allows you to create a plan, ask questions, and get support from an online community.

QuitTobacco. Make Everyone Proud (For Military Personnel) 
This site, sponsored by the U.S. Department of Defense, helps U.S. service members and Veterans quit tobacco.

CDC: Smoking and Tobacco Use 
This site provides quitting advice, the latest research and news on tobacco use, publications to order, and an array of useful links.
This site is also available in Spanish.