Gonna get one this winter, for both the new p-patch plot and Davi and Wojtek's garden. Carol Deppe says to get it from the folks at Peaceful Valley Farm Supply, and buy the interpretive booklet, too. $50 total. Ask for an analysis for nitrogen, phosphorous, potassium, sulfur, calcium, and magnesium. Also ask for an analysis of anything commonly known to be missing or present in toxic amounts in your region. Send in the sample 6 weeks or more before you need the results. Collect several soil samples from different parts of your land and pool them. Collect from below a sod cover. Exclude leaves and roots.
The University of Massachusetts Soil and Plant Tissue Testing Lab offers them for quite a bit cheaper, but without the guide.