Metafilter has a great thread discussing free learning webpages.
One outstanding site, the Research Channel, webcasts educational video 24 hours a day. Their extensive video archive can be browsed by title and by subject.
The Math Archives gathers links to sites with tutorials and notes for a broad range of areas in mathematics.
The University of Indiana has a great portal for music sites.
The London School of Economics and Politics offers transcipts to many of their events and lectures over the past eight years.
SUNY-Albany's Talking History has archives of their show going back to 1997.
Wired For Books has posted many of Don Swain's CBS radio interviews with writers such as John Updike and Allen Ginsberg.
Also see the Wired For Books' Kids section for well-produced audio narrations, such as a full length Alice and Wonderland. If you're studying French, German, or Japanese, you can practice with The Tale of Peter Rabbit.
The list has also been turned into a list on Christopher D. Sessums' PBWiki. Be warned that not everything on this list is actually free (i.e. the great, but not free Recorded Books)