This, possibly more than anything else presented so far, is something that will truly change the world as we know it.
Podcasting allows anybody to live the old Mickey Rooney and Julie Garland fantasy and "Put on a show". Aspiring playwrights and other writers, wannabe actors and actresses, teachers and amateur enthusiasts of all stripes can put on a production and potentially reach an audience as big as any of the major networks. And, thanks to moviemaking, music composition and CGI software, the at-home productions can reach suprisingly good quality. Education and entertainment where ever you go and whenever you want it.
Of course, that same ease of access can work against the people producing the podcast as well. When I looked under the comedy section of Podcastalley, there were nearly four thousand podcasts. I hardly knew where to start.
For libraries, I see the most direct applications being with the special interest groups such as the writer's club. But, this can be used by any group with creativity and an urge to share it with the world.