FlightGear Flight Simulator: free open-source multiplatform flight sim
A circuit simulator with graphical user interface (GUI)
X-Plane plugin that displays a tablet to aid VR usage
VHDL 2008/93/87 simulator
Fast PlayStation 1 emulator for x86-64/AArch32/AArch64
Simulate chemical processes using advanced thermodynamic models
PICSimLab is a realtime emulator for PIC, Arduino, STM32, ESP32, ...
Uruk GNU/Linux fast, simple and strength GNU/Linux distribution
Component, CA, and CCA models; superdense time, DB repo, testing, etc.
An advanced network simulator to design and configure virtual networks
Soft-body physics simulator
Real Time Electronic Circuit Simulator.
Virtual Pipe Organ Software
Data Compression Simulator for E-Learning:
Android, UIQ 3.0, Series 60 Edition 5 open-source software
Combat Flight Simulator for LINUX. WW2. Network and VOIP. Open-source.
Air traffic control tower and radar simulator (solo + multi-player)
Physically accurate and validated GPU ray-tracer