Artificial Intelligence Systems in Routine Clinical Use
Hewlett-Packard Laboratories in Bristol, UK, sponsors this site which outlines artificial intelligence systems in routine medical use.
http://www.coiera.com/ailist/list.html

SASS - Speak and Spell simulator for windows
Simulator of the speaking cousin of the TI-99/4A.
http://sass.retrogames.com/

Ant Farm Simulator
A VB based simulator of food-gathering behavior of ant colonies. Executable and VB source code are available.
http://www.geocities.com/chamonate/hormigas/antfarm/

SCJP Simulator
Offers an exam simulator with provision to add more questions.
http://www.examsguide.com/scjp/freesimulator.html

FlightGear Flight Simulator
An open-source, multi-platform, cooperative flight simulator development project. Source code for the entire project is available and licensed under the GNU General Public License. The goal of the project is to create a sophisticated flight simulator framework for use in research or academic environments.
http://flightgear.sourceforge.net/

RDS-PLUS
ECD RDS-PLUS Router Delay Simulator Plus
http://www.bomara.com/ecd/rds-plus.htm

Flight Gear Flight Simulator
The FlightGear flight simulator project is an open-source, multi-platform, cooperative flight simulator development project. Source code for the entire project is available. (OpenGL)[OS Independent]
http://www.flightgear.org/

Avocet Big Bang Simulator
Avocet's AVS68K, 68xxx Family High Level Simulator includes a debugger, mini-assembler and disassembler.
http://www.avocetsystems.com/company/techshee/asheets/bbsim.html

PIC Simulator IDE
PIC Simulator IDE with Basic Compiler, Assembler, Disassembler and Debugger
http://www.oshonsoft.com/pic.html

Z80 Simulator IDE
Z80 Simulator IDE with Basic Compiler, Assembler, Disassembler and Debugger
http://www.oshonsoft.com/z80.html