SimQuest is our oldest simulation-based learning software. It features an authoring system for instructional computer simulations. With SimQuest you can create a simulation by writing equations such as:
dx/dt = v dv/dt = a a = F/m F = -k*x
and create an interface around this simulation. Instruction comes in the form of assignments and explanations. On www.simquest.nl you can see what is possible and download the system.
At the level of ideas however, SimQuest is still fit and it has also grown with its time. Simulations are now stored as XML and we have a java-based player for simulations.
We make this project open source from the start. If you are interested, which may be because you think simulations in education are cool or you are seeking an interesting programming challenge, you may even contribute. Have a look at the code pages and contact us of you want to go along.