I found this Podcast Tolkien at Oxford to be quite interesting (only 2 episodes so far)

Tolkien and Languages: Ancient and Invented
Stuart Lee and Elizabeth Solopova

Tolkien and the Oxford English Dictionary: 'The Ring of Words'
Stuart Lee, Peter Gilliver, Jeremy Marshall, Edmund Weiner

There is another Podcast on this page which people may also find interesting (Oxford University: Podcasts from Medieval English lectures)