There were posts about soil testing in the alfalfa tea thread, so I thought I would kick out the topic by itself - this is just one of those "for what it's worth" stories:

Until 2001 I taught at a regional high school with an attached technical/vocational school. The horticulture/ag program offered soil tests done by a class under teacher supervision. The students prepared instruction sheets explaining how to collect the soil sample, with little bags. They charged a dollar or two, but of course accepted donations. The money was used for FFA trips.

These were very simple tests, acidity and a few other thngs were tested that I can't remember. But if there is a school horticulture program near you, it might be worth checking them out.