Faith by Hearing (faithbyhearing.wordpress.com)
Faith by hearing provides a large index of sermons and lectures from various sources. The audio is sorted by book of the bible, doctrine, part of history for historical lectures, speaker, topic and type of presentation so you should have no trouble finding something of interest.
Worldwide classroom (www.worldwide-classroom.com)
Worldwide classroom provides the audio for over 20 university level courses from Covenant Theological Seminary for free. For some courses transcripts and course notes are also provided.
Passion Messages Podcast (268media.com/passionmessagespodcast)
Messages from Louie Giglio, best known for his role in the Passion conferences.
The Open House (theopenhouse.net.au)
The Open House is an Australian radio show that plays interviews on life, faith and culture with an assortment of interesting people from a variety of fields.