Actually, I was coasting after cresting a small hill, and was probably doing ~40mph.
Looked to be a 200lb doe. I stopped about 40-50 yards down the road to survey damage, and kick the wheelwell off the tire, and couldn't find the deer. I suppose she limped into the woods to die. I know I at least broke it's leg!
My girlfriend hit one a week later with her truck. It's that time of year - be careful out there! And support your local hunters!