Benchmarks for excellent teaching

I recently received in the mail a catalogue from The Great Courses. It took me a while to realise that this is the Australian incarnation of what used to be called The Teaching Company. I first encountered the latter at the recommendation of my father-in-law. The company sells DVDs, and CDs of some of the best undergraduate lecture courses from (mostly) US universities. I previously had my department buy a copy of The Joy of Science, 60 lectures on science for non-science majors. Just watching a few lectures challenged the clarity and simplicity of my own lectures.
On the personal side, I have really enjoyed listening to CD's of most of the series How to listen to and understand great music. I was challenged to make my teaching more interesting.
Don't balk at the prices because they often have 70% off sales. For example, right now the Chaos course by Steven Strogatz and the Quantum Mechanics course by Ben Schumacher are on sale.