Thanks to Russell, who tipped us off to the fact that John Piper has provided some excellent missions sermons and panels, originally staged at a missions conference in 2011, at…

http://www.desiringgod.org/resource-library/conference-messages/by-conference/2011-national-conference

Speakers include Louie Giglio, Jason Mandryk, Greg Livingstone, David Platt, and, of course, Piper himself. Excellent stuff. (Thanks Russell!)