Ive been carrying a Colt Cobra in a Ankle holster. Its a Renegade, its so comfortable you can forget its on. I have worn it with shoes, hiking shoes and 6" tall boots.

Forum poster Sipowitz speaks highly of this and turned me on to it.

Edit... When wearing low shoes I keep it slightly rotated gun rearward. This is so the barrel does not hit my ankle bone. Ouch....