A series of eight podcasts by Norman Fischer on Dogen's teachings on Zazen. I have only listened to the first one so cannot vouch for quality but he is usually pretty good.
Further information (after listening to the second podcast): Roshi is talking about the 28th fascicle of Shobogenzo - Zazen Shin (The Point of Zazen), p303 in Kaz Tanahashi translation. This fascicle begins with the well known dialogue between Yaoshan and a monk:
Yaoshan, Great Master Hongdao, was sitting. A monk asked him, "In steadfast sitting what do you think?"
Yaoshan said, "Think not-thinking."
"How do you think not-thinking?"
Yaoshan replied, "Beyond thinking"
The second podcast has, in my opinion, an excellent explanation of what is meant by non-thinking or beyond thinking.