I sent some soil samples to UMass on Thursday. I did this last year as well; UMass sent back a report which I used when I planted my blueberry hedge.
This year, thanks to some guidance from the Western Massachusetts Master Gardener's Association, I sent several samples of soil to the lab - one for my perennial bed, one for my vegetable garden and fruit trees, and one for my blueberry hedge.
I dug about a cup of soil from different spots in each of the beds. I put everything in plastic baggies, filled out the form to indicate the tests that I wanted ("basic" and "organic matter"), indicated what I am trying to grow, and sent it off (with a $37.00 check, for 4 tests and reports).
The only step that I didn't do was spread the soil out on a sheet and let it thoroughly dry. I don't know how important this is - I'm hoping that it's not.
UMass Soil and Tissue Testing Lab - http://www.umass.edu/soiltest/