The AbstractAlgebra package is a freely available complement to the book Exploring Abstract Algebra with Mathematica. The package supports working with (finite) groups, rings, fields, and morphisms and functions related to each of these objects. There are a large number of built-in groups (including such standard groups as $Z_n$, $U_n$ (units of $Z_n$), $S_n$, and $D_n$, as well as direct products and quotients of these) and rings (including $Z_n$, Boolean rings and lattice rings, as well as polynomial, matrix and function extension rings). One can also create functions between groups or rings and investigate if these are morphisms.
Seven different packages related to mathematical physics; a package for GR-type tensor algebra, one for Virasoro algebra, one for algebra with Grassman variables, a package for Polchinski theta-function conventions, a package specialized at inverting diagonal matrices by inverting each diagonal entry separately, and two packages that deal with approximations to the Ricci-flat metric on the algebraic Calabi-Yau manifold.