Spreadsheet Add-Ins and Interest Groups
David Hartvigsen has developed an Excel Add-In called SimQuick for process simulation.

Microsoft Excel Solver:

Help for Microsoft Excel Solver Users from Frontline Systems

Premium Solver, from Frontline Systems
INSIGHT Business Analysis Tools for Microsoft Excel from Sam Savage.
OR/MS add-ins for Microsoft ExcelPaul Jensen.
xlstat - statistics add-in.
Spreadsheets, Mathematics, Science, and Statistics Education lists spreadsheet add-ins, among other things.
Lindo Systems, Inc.
@Risk, from Palisade Corporation
Crystal Ball, from Oracle.

Web-based Software
Robert J. Vanderbei's homepage has links to several Java applets for teaching linear programming.
MIT’s Open Courseware (OCW) is a web-based publication of virtually all MIT course content. OCW is open and available to the world and is a permanent MIT activity.
tutOR: an extensive collection of JavaScript-based tutorial modules.

Stand-alone Educational Software
Proware Corner - Freeware for Industrial & Systems Engineering, Operations Research, Production & Operations Management and Manufacturing & CAD/CAM. Maintained by B. Khoshnevis.
Production Management Trainer (PMT) - educational software system for production and logistics.
The Mentor Project