REDUCE Computer Algebra System - Bibliography, documentation, available packages, online demonstrations and ordering information for versions from 3.8 onwards. - http://www.reduce-algebra.com/
The Reduce Computer Algebra System - An interactive program designed for general algebraic computations of interest to mathematicians, scientists and engineers. - http://www.zib.de/Symbolik/reduce/
REDUCE - Program for general algebraic computations of interest to mathematicians, scientists and engineers. Over 20 years old. Comes with full source code. Site even lets you run the program remotely, in order to test the product. - http://www.uni-koeln.de/REDUCE/
REDUCE IDE - Integrated Development Environment for the REDUCE computer algebra system within the GNU Emacs editor. Free download, documentation. - http://centaur.maths.qmw.ac.uk/Emacs/REDUCE_IDE/