bellywomen.net, alace.org
Ask at the yoga studio, at the health food store, at the prenatal massage that you treat yourself to...
Also, look at all those websites that are listed, and read, read, read. There is tons of valuable information available on the sites. That'll really help you decide if having a doula attend your birth is what's right for you. There are so many benefits, if you find a doula that is a great fit. Good luck in your search!