I have discovered some iTunes U ranking pages for the maths videos and maths collections.
See (free iTunes software required)
for the “top 200” iTunes Maths Collections
for the “top 200” maths video downloads.
What “top 200” means on iTunes is not obvious. It apparently involves a complicated combination of factors. Does anyone have any detailed information on this?
The top downloads are currently dominated by: Harrisburg Area Community College, especially Susan Cooper; MIT, especially David Jerison; Cambridge University, especially James Grime; and a variety of videos from Imperial College London.
Apparently James Grime recently passed 10,000 YouTube subscribers for his singingbanana collection. (See http://www.youtube.com/user/singingbanana)