I have looked at the links you guys sent out, and now I have started to look at a single speed 29" as I am 6'1" and it would be fun to ride a bike of that size. It sees the basic models are $400-500.

I also found a Sheldon Brown article on building up a single speed MTB with a full discussion of the ups and downs of frames, tensioning the chain, and choosing the gear ratios. Pretty good, but makes me want to buy one more than build one.

The Dirt Jumper sure looks sweet.