George's Rocketry Pages. George Gassaway's excellent site, including plans, contest event tips, scale data, videos, and much more.
John Boren. Model rocketry and model airplanes by John Boren, head of the Estes R&D Department.
Meatball Rocketry. The model rocketry pages of the Tschirhart family and the Meatball Rocketry Team (NAR T-684). Contains scale data and photos as well as building tips, R&D articles, and more.
ShroudCalc. A nice Java script site for calculating conical shrouds. By Robert W. Blaske.
Ultimate Paper Rocket Guide. Excellent templates for paper rockets that you can build and fly. Tremendous variety of models including Soyuz, Saturn IB, and Saturn V.