The tools in the Industrial Engineer and Operations Research tool bag is increasing with the advances of software systems. In the past the tools were relegated to proprietary software that would cost an organization licensing fees, software updates, and support services. Yet there is a shift in thinking in how software is developed, delivered, and administered to the masses. That shift is in free and open source software. This free software movement has shifted the thinking that good software need not be copyrighted and licensed for proprietary distribution. Instead software should be made freely to the masses to use, distributed, and even improve upon.
The free and open source software movement has even made its way to Industrial Engineer and Operations Research tools. There are many proprietary equivalents that can be found in the free software realm. Most of which will even work on a Windows platform. I have listed some of these software tools in a equivalents table.
Microsoft Excel ---> OpenOffice Calc, KOffice KSpread
Spreadsheet LP Solver
Excel Solver ---> OpenOffice.org Calc Optimization Solver
Math Programming Software
AMPL, CPLEX, GAMS ---> GLPK, OpenOpt
These are but only a few equivalents. You can see more free and open source equivalents to all sorts of software on the following links.
The Table of Equivalents
LinuxQuestions.org equivalents table