Main page at MIT, Scheme's birthplace; short list of implementations, some general documentation, information on the MIT Scheme implementation, some random links.
By R. Kent Dybvig; Prentice Hall, 1996, ISBN 0134546466, 2nd edition. Reference book, describes R5RS Scheme in style similar to K and R [Online full text version].
A collection of resources for the Scheme language. Information on all aspects of Scheme: implementations, papers, and code. Maintained by the Rice Programming Languages Team, the folks behind MzScheme and DrScheme.
Publishes and carries excellent educational materials, including books, using the Scheme programming language. Has Windows and Macintosh Scheme interpreters and a Scheme-driven state-of-the-art solid modeler.