Q&A, forum about 3D Printing : 3DPrintForum (Dutch)
FreeCad (also on OsX and Linux)
3DBuilder
LibreCad (also on OsX and Linux)
3D Crafter
BlocksCad (online in browser)
Leopoly (online in browser)
SculptGL (online in browser)
TinkerCad (online in browser)
Wings 3D (also OsX and linux)
Antimony (Linux and OsX only)
eMachineShop
Fusion3D (also on OsX)
MeshMixer (also on Osx and Linux)
SelfCad (online in Browser)
SolveSpace (also on Osx and Linux)
BrlCad (also on OsX and Linux)