Caroline Gibbs is the woman who prescribed me testosterone. She's actually really awesome and you can tell that she knows what she's doing. Not only did she help me as far as transitioning, but she helped me deal with a lot of issues at school that I wouldn't have known how to take care of without her assistance. Literally anything about transitioning is what she takes care of - not just the diagnosing part.
She also gives referrals to a great internist named Cynthia Glass. She's a lovely woman and is extremely sympathetic to the trans community. She is, by far, the friendliest doctor I've ever gone to. Oh, and her office and Caroline's are in a reasonable driving distance, so that's a plus.