Autolev 
An advanced symbolic manipulator for engineering and mathematical analysis. 
FEMLAB 
A scripted finite element model builder and numerical solver. PDE solutions, Inc. 
FlexPDE 
A generalpurpose Software System for obtaining numerical solutions to
the coupled sets of partiar differential equations found in physics, chemistry, etc.

GAMS 
Generalized Algebraic Modeling System.
GAMS is designed for modeling linear, nonlinear, and mixed
integer optimization problems.
It is available on PCs, workstations, mainframes, and supercomputers.

IDL 
The Interactive Data Language is software for visualization,
data analysis and crossplatform application development.
They may have gone out of business, as the link does not seem to work.

ILOG CPLEX 
JRules for highperformance, flexible optimizations.

JMP 
Statistical discovery software 
MacKichan 
Scientific Workplace and other products for producing mathematical documents.

Maple 
Mathematical computation software 
Mathematica 
Integrated technical computing system: Interactive calculation,
visualization tools, and a complete programming environment 
MathSoft 
MathCad computing environment. 
MathType 
Create mathematical notation for word processing, LaTex, etc. 
MathWorks 
MatLab and Simulink computing and modelling environments. 
NAG 
Numerical libraries for Fortran 77, Fortan 90 and C 
NCAR 
Mathematical and plotting software. Free. 
Numerical Recipes 
Software from the famous book 
Octave 
GNU Octave is a math package for numerical computation.
It is not intented as a clone of MatLab, but it shares much of
the notation. 
Origin 
An analysis package that offers a suite of data
analysis and custom utility development tools. 
Rogue Wave 
IMSL and PVWAVE. 
Scilab 
The SciLab package of software for statistical analysis. 
StatSoft 
Statistica 
Tecplot 
General purpose scientific plotting. Also Tecplot Edge. 
UTS 
TK Solver and other tools. 
UNSCANIT 
Converts scanned graphs to (x,y) data. Silk Scientific. 