The xRC Simulator or Autodesk's Synthesis allow First Robotic Competition teams to drive simulated robots around the season's field, allowing early practice with driving, viewlines, and team strategy.
While Synthesis seems to provide higher fidelity, xRC seems a little more user-friendly to me.
Installing on Windows is straightforward, but if you install on the Mac, you are likely to get a "Can't open application 'xRC Simulator'" that is different than the normal "Unknown developer" security warning. To fix it, open a terminal, switch to the directory in which you've unpacked the xRC Simulator and run:
chmod +x xRC\ Simulator.app/Contents/MacOS/xRC\ Simulator
This means "Change the mode to 'Executable' of the file at {path}". After running this, you can close the terminal and run the xRC application. You will probably get the normal "Can't open this application because it's from an unknown developer," error. Open Settings | Security and find the checkbox that allows you to run the package.