DOS Beowulf
Simple, inexpensive Beowulf supercomputing clusters for DOS
https://dosbeowulf.tripod.com/
PARI/GP Development Headquarters
Science, Math, Number Theory, Software - PARI-GP Download Area. Latest versions in source and compiled form.
http://pari.math.u-bordeaux.fr/
Apfloat Home Page
Science, Math, Number Theory, Software - apfloat. High-performance arbitrary precision arithmetic package for C++ and Java.
http://www.apfloat.org/