I'll be working for 7 months in Eastern South Dakota in Brookings. I'm willing to take a bit of a drive to get to some decent mountain biking. Are there any recommendations?

Also, is there any good riding in the Badlands, it seems like a place that could really be one of those mountain biking meccas given the support.

Thanks.

You pretty much have to drive to the Black Hills. The drive is worth it because the Black Hills has AWESOME mountain biking. If you can check out the Fat Tire Festival starting May 23rd.
A couple links:
http://www.acmebicycles.com/
http://bhmba.org/
http://blackhillsfattirefestival.com/