FlightGear Flight Simulator: free open-source multiplatform flight sim
Qt Visual Graph Editor
Creates 3D models from photographs
3DimViewer is a lightweight 3D viewer of medical DICOM datasets.
Graphical Interface for Medical Image Analysis and Simulation
Multiplatform tool for batch image conversion
Multiplatform GUI to losslessly compress JPEG files
3D interactive application library
Steghide GUI is perfect C++/Qt app for embedding and extracting data
Image Viewer and Editor, simple but powerful enough for everyday use