Arkansas
In Arkansas, there are apparently more diamonds in the ground than in Liberace's closet. So many that they're practically giving them away. Show up at Crater of Diamonds State Park, a 120-mile drive from Little Rock, and you're free to roam the grounds and dig for precious stones at the only diamond-producing site in the world that's open to the public. Most of the stones visitors take home aren't of high enough quality to be truly valuable, but a few visitors have hit it big. In June, a 13-year-old Missouri girl pulled a 2.93-carat whopper out of the dirt. That should pay for a few weeks of college — or these days, a few hours, at least.
Rental: $11 for an advanced diamond hunting kit (which includes a folding shovel, screen set and a 3.5-gallon bucket).