Building interactive VR simulators for training could be an expensive project. Second Life could lower the costs since it's relatively easy to build interactive objects and buildings for avatars in this 3D virtual world. Add a motion-sensitive controller like the Nintendo Wiimote and the simulator is ready for training!
Wired has a nice article discussing the possibilities: Wii + Second Life = New Training Simulator. Imagine the setup with a nice 3D display and you have a full low cost VR simulator environment!