S-Plus

ESS: Emacs Speaks Statistics
Package for GNU Emacs, provides command-line, editing and transcript support for S-Plus on Unix, Windows.
http://www.stat.math.ethz.ch/ESS/

A Handbook of Statistical Analyses Using S-Plus
By Brian S. Everitt; CRC Press, 2001, ISBN 1584882808. For applied statisticians, researchers, students. Introduces possibilities of S-Plus, S-Plus 2000, S-Plus 6, for data analysis.
http://www.crcpress.com/shopping_cart/products/product_detail.asp?sku=C2808

StatLib
Software and extensions for the S (S-Plus) language.
http://lib.stat.cmu.edu/S/