Willa Gayle,

The Prometric testing centers are located all over the place (do you have a Sylvan Learning Center near you?). I still had to drive 3 hrs each way, but my boys were very appreciative and we made a day of it. http://www.prometric.com/Default.htm
The way to "get" to test is through the talent searches. In order to get into a talent search to register for a test, your child either has to have IQ test data, tested high on standardized tests that schools give in the spring, or get a teacher's recommendation/portfolio. Once you meet that criteria and a small fee, you're given the opportunity to take "advanced level" tests. I don't think you can just register to take the test on your own. The SCAT is expensive (maybe $80) plus johns hopkins fee of maybe $25. The test is short (about 45 minutes or less). This is a good start for 2-6th grades. The EXPLORE test used by Duke TIP and Rocky Mt Talent Search is for 5th-6th graders, takes about 2.5 hrs, and costs $56 (plus talent search fee). After 6th grade, it's SAT/ACT, but going through the talent searches is a good idea because they give you a report showing how your kid did compared to the rest of the population. Very cool.