Numerical Methods and Software

NCAR software.
Vector Signal Image Processing Library
Numerical algorithms from Arizona State Univ. (Hans Mittlemann?).
And, or course Numerical Recipes.
Gnu Scientific Library.
MathTools.net
Object-Oriented Numerics
check Google for more from Drexel, Indiana, ...
Home page for James Demmel
GAMS.
NIST has lots of links and a good search engine for mathematical inquiries. Check out DLMF, the Digital Library of Mathematical Functions.
NetLib
The Math Forum.