Regent College is offering 451 audiobooks for free right now. I think that all of them are one-session lectures, many by leading evangelicals of the day.
Regent is known for selling many different lectures. Most of them are what I consider to be very expensive. Offering the free lectures is quite an extraordinary offer, not only because of the quality of the speakers, but also because of the sheer number of the free lectures!
https://www.regentaudio.com/collections/free. Scroll down to just beyond the Vancouver First Baptist Church Sermon archives.