NASA has released a simulation of the Mars Curiosity rover that allows folks to drive around the Red Planet as part of the three-year anniversary of the rover's landing. You can also drill into a rock, manipulate instruments, and even take a selfie. Yes, you can take your own (simulated) selfie on (simulated) Mars.
The simulation itself is fairly robust. Users can point the rover in a variety of directions and watch it crawl across the dirt, watching what it sees from a number of different devices like the front hazard camera all the while.
This 3D version of Mars is based on actual data from Curiosity and NASA's Mars Reconnaissance Orbiter (MRO), meaning that what you're bumbling around in is actually how we see Mars. Unfortunately, this also means that they haven't exactly rendered the area where Curiosity hasn't gone, so there's no way to take this baby off the beaten path.
That didn't stop me from getting the thing to fly, however.
NASA also released Mars Trek, which provides detailed visualizations of Mars based on 50 years of data. Which is, you know, neat, but not the same as personally piloting a rover around an alien world.