The Touring Archives at phred.org -- probably the best touring resource available on the Internet today. What's more, it's interactive -- you email questions and responses, which are sent to everyone else on the list. An invaluable resource.
The Adventure Cycling Association is a non-profit organization that creates bicycling routes throughout the US. High-quality, low-price, and serving the bicycle touring community. An excellent resource.
Ken Kifer's Bike Pages is a wonderful informational site. Make sure you check out the link to bicyclinglife.com, which has useful information for beginning tourers and cyclists.
Sheldon Brown's Bicycle FAQ contains a mind-numbing amount of obscure bicycling information. Everything from gear ratios to glossaries, with explanations of difficult maintenance and repair techniques.
crazyguyonabike.com -- the narrative I visited the most when planning my bike trip, and the one that evokes the most memories now. An excellent account of Neil Gunton's solo TransAm ride. Note: he has expanded the site to host other journals.