Texas A&M's soil testing lab for this. There's my plastic bag of at least two cups of soil.
I'm doing this mostly out of scientific curiosity, and not because I think there's anything wrong with my soil (though I guess I could be surprised). I just thought it would be kind of interesting to get some sort of baseline, and maybe even later have it tested again to see if I've at all improved it (if I do end up living in this house for much longer).
It doesn't cost all that much. The actual fee for the sample ranges from $10 - $25 depending on how many things you want them to test. I am tempted to go all the way and get the $25 test done, which measures pH, N, P, K, Ca, Mg, Na, S, Zn. Fe, Cu, Mn, conductivity (I'm not sure what that is), and organic matter.
Then this shipping will cost about $5 because soil is heavy. I'm trying to cram it into a Priority Mail small flat rate box. It looks like it will just barely fit.
I didn't quite follow the directions on how to take a soil sample given by A&M. They say to take soil samples from different parts of the area you are testing and mix them up, being sure to get samples from areas of different soil types. I'm more interested in what my baseline soil is before meddling with it, so I was careful to sample an area that I have NOT messed with much yet (by adding compost, fertilizer, etc.), and I also avoided the areas of my garden that have a lot of sand, due to once being under an above-ground swimming pool.
I hope the results are interesting. Texas A&M gives the recommended NPK amounts for various crops, which is interesting in itself to compare different crops (like how regular potatoes apparently need way more nitrogen than sweet potatoes), and should be even more interesting once I get my results.