John Piper and Kent Hughes - BiblicalPreaching.com
http://www.DesiringGod.org

Douglas Wilson - Weekly Sermons on Covenant, Family, etc.
http://www.christkirk.com/Sermons/RATable.asp

Mongergism MP3 Links
http://www.monergism.com/...

Covenant Seminary Online Courses
http://www.covenantseminary.edu/...

Covenant Life Church (Josh Harris)
http://www.covlife.org/tools/sermons.php

7000 Sermon Downloads
http://www.sermonindex.net/modules/mydownloads/

MP3 Audio Books, including GK Chesterton's Orthodoxy
http://www.freechristianaudiobooks.com

Ottawa Reformed Presbyterian Church, Richard Ganz
http://www.rpcottawa.org/sermons.php (RealAudio)

Mount Olive Tape Library:
http://www.sermonaudio.com/...

Heritage Netherlands Reformed Congregation - Dr. Joel Beeke
http://www.hnrc.org/gr/Sermons/sermons.asp

Valley Bible Church (1000+ sermons)
http://www.valleybible.net/cgi-bin/sermons.pl/

100,000+ free MP3 sermons
http://www.SermonAudio.com

Grace Orthodox Presbyterian Church, Costa Mesa, California
http://www.grace-opc.org/download.htm