Thanks to Richard Hawkins & his excellent Bluegrass Ireland Blog for bringing this set of 3 YouTube lessons to my attention.
AND - for clawhammer-banjo players who want to learn the highly regarded Round Peak style, FOAOTMAD draws attention to an excellent set of free video lessons from Tom Collins of the New Hot Times string band. Lesson 1 can be found on YouTube (see below), and the following lessons can be reached from there. Highly recommended.