Macaulay is a program for computations in algebraic geometry. Math Source is Wolfram Reasearch's public FTP archive. Maple is Maple's public FTP archive. MuPAD is a multi-purpose program for performing symbolic computations. Simath is a programming library for computations with elliptic curves and number fields.
Singular is a program for computational algebraic geometry.
Waterloo is a public FTP archive containg news, fixes, and add-ons for Maple.