If you've never heard of crawlspace encapsulation a quick internet search will enlighten you... quickly. The basic principle is to completely cover the ground of the crawlspace with a heavy vapor barrier and even run it up the walls to block any moisture that might come in through the concrete blocks.
Step 1: Why?
I wanted to make sure there were no future problems and that's when I first read about encapsulation. I didn't know what it might cost though. To give you some idea why I chose to do it myself:
After a woman I work with heard about this she had someone come and do it for her and paid $8,000.
I paid about $300 to do this 30' x 25' space. That's a savings of nearly 97%. Boo. Ya.
I think I made the right choice.