The Chinese Outpost is a great Chinese Language learning and culture site, developed by an American, Mark Baker. He grew up on a farm in Ohio, and now lives near Seattle, Washington with a job in the field of technical communications. He once taught in China during 1993 and 1994, and currently goes back there with his native Chinese wife and their two pre-schoolers. You can even read his blog of 2006 trip to China online.
The Mandarin Chinese Tutorial in the Chinese Outpost is a well-written and detailed introduction of the major features of Mandarin Chinese language, which aims to give you a broad overview of fundamentals in the pronunciation, characters and grammar of Mandarin Chinese. After finishing it, I feel sure that you, with a solid basic understanding of the Chinese language, would not plunge into Chinese language learning like blind men trying to size up the elephant.
Plenty of very interesting topics and links, such as Personals to find language learning partners and Music to listen to traditional Chinese music by erhu or bamboo flute, are also provided.