Here's a cheapie:

http://holeshotrp.tripod.com/

I would say it is a Brake Hp Dyno. You drive an elctric motor as a generator and add electrical load (reduce resistance) until the engine maintains a certain rpm at WOT. You have to repeart this at various speeds to get a graph.

A better method is to use an intertial dyno. Here's a Youtube video of a homemade one:

http://www.youtube.com/watch?v=JYt_u0URcks

Or you can buy an intertial one, but as above, they can be pricey:
http://www.rcdynosystems.com/

However, at a mere (paltry?) $1700 USD, it might be afordable (too pricey for me, but better than $6K). Maybe you can buy one and charge your friends $10 a dyno run for their vehicles?