http://www.dharmaseed.org/ offers Dharma talks from monastic and lay teachers, mostly Thervadin, some Mahayana. Many Spirit Rock Meditation Center teachers are recorded here.
http://www.audiodharma.org/ Offers the teachings of Gil Fronsdal and associated teachers from Insight Meditation Center in Redwood City, CA.
http://www.buddhistinsightnetwork.org/dharma-study Dhamma and Buddhist studies offered here.
http://www.dhammatalks.org/ Thanissaro Bhikkhu, a prolific translator of Pali texts, offers Dharma talks/