Finite Canonical Commutation Relations
A working paper on FCCR nxn matrices as local kinematical replacement for CCR, and representations by pxp matrices over Galois fields.
http://graham.main.nc.us/~bhammel/FCCR/fccr.html

CMAT
A matrix calculator program, written in C. Calculations can be performed on matrices with complex rational coefficients using exact arithmetic routines, as well as on matrices with elements mod p.
http://www.numbertheory.org/cmat/krm_cmat.html

Homogeneous Transformation Matrices
Explicit n-dimensional homogeneous matrices for projection, dilation, reflection, shear, strain, rotation and other familiar transformations.
http://www.silcom.com/~barnowl/HTransf.htm

Matrices
The 1934 classic "Lectures on Matrices" by Wedderburn in scanned PDF.
http://www.ams.org/online_bks/coll17/

The Matrix Computation Toolbox
Nick J Higham - School of Mathematics and Manchester Institute for Mathematical Sciences, The University of Manchester, UK
http://www.maths.man.ac.uk/~higham/mctoolbox/

Hadamard Matrices
A library of Hadamard matrices maintained by N. J. A. Sloane.
http://www.research.att.com/~njas/hadamard/

VisiCube
Exploratory data analysis (EDA) application for Windows. Uses plots such as Box Array, Box Plot, Quantile Array, Scatter Plots (2D, 3D and Matrices), and Time-Series (Arrays and Matrices). EDA findings can be saved and revisited using a visual library. Full functionality shareware except for publication capabilities, which must be purchased.
http://www.datamology.com/

LINPACK
A collection of Fortran subroutines that analyze and solve linear equations and linear least-squares problems. The package solves linear systems whose matrices are general, banded, symmetric indefinite, symmetric positive definite, triangular, and tridiagonal square. In addition, the package computes the QR and singular value decompositions of rectangular matrices and applies them to least-squares problems.
http://www.netlib.org/linpack/

Check or Generator Matrices of Some Linear Codes
Examples for q up to 9.
http://www.mathi.uni-heidelberg.de/~yves/Matritzen/Codes/CodeMatIndex.html

Ted Spence's Home Page
Classification of Hadamard matrices and designs.
http://www.maths.gla.ac.uk/~es/