The guys over at TekPub make some great screencasts, and their 'Concepts'-series covers both unit testing and BDD.
They just released a new screen cast "Full Throttle: TDD with Brad Wilson" for $12 where Brad works on a billing subscription system using TDD.
Rob Conery also throws in some curve balls during the session to help show how TDD can adapt to change. Unfortunately, these are single episode series so there is only one, but it is an hour long.
