Chinese language learning materials are available from several vendors including Fairfield Language Technologies, Penton Overseas, various bookstores and computer software vendors, etc. See Foreign Languages.
ASIA KIDS (http://www.AsiaforKids.com) carries many Chinese language materials (Cantonese and Mandarin) for all ages; also carries Rosetta Stone materials.
LEARNABLES, Chinese, is available from International Linguistics (http://www.learnables.com); for ages 7 and up.
TEACH ME, Chinese (Penton Overseas), audiocassette tapes, for kids ages 2 - 12, are available through distributors such as Early Advantage.
On-line resources include:
ABOUT.COM's Chinese Language area (http://chineseculture.about.com/culture/chineseculture/cs/language/index.htm) includes links to various Chinese language related resources, etc.
FREE CHINESE LESSONS (http://www.freechineselessons.com/) FREE online lessons take you from beginner to intermediate.