http://www.grassrootshealth.net/ You just have to answer some easy survey questions. You can enter for twice a year testing for five years, or a one time test, or two tests in one year, with each home test costing forty dollars. This is a non profit organization. You can check out the board members, mostly PhDs and MDs affiliated with California universities.
I've looked online for prices and this is about 30% cheaper than the average Vitamin D home testing. Well, you do have to send the strip into a lab, but you can do the test at home. So, it involves no doctor's appointment. In NY state this isn't allowed, apparently.
I just entered my husband in the program. His dad actually had rickets as a kid, and yes, he was raised in the south and played outside a lot. There may be something hereditary going on with the ability to make Vitamin D.
Mostly I think this organization is trying to raise awareness, and to give a push for higher RDA of Vitamin D, because of the strong evidence from epidemiology that low Vitamin D levels are linked to many chronic health problems. Our current recommendations only involve avoiding rickets, which happens only at extremely low Vitamin D levels.
Here is a chart of the many conditions associated with low levels of Vitamin D in studies--several types of cancer, ms, type 1 diabetes, fractures, falls, etc.
http://www.imminst.org/forum/index.php?act=attach&type=post&id=6065