Radio  

Oldradio.com Broadcast Archive - Reputable and very comprehensive; includes a list of the first stations in the US and lenghty bios of radio pioneers.

Television and Radio History - Good overview of radio history, including major breakthroughs; includes timeline.

History of Communications - Radio - The FCC's page on the early development of radio, with links to detailed articles on the Tesla Coil and other major innovations.

United States Early Radio History - Links on various sections take you to periodical articles from the appropriate time period.

Old-Time Radio: Commercials - Old-time.com's large archive of radio ads from the 1920s through the 50s. Click on the small red rectangle to hear ads in WMA format; surf to other components of their radio section.

Library of American Broadcasting - Page for University of Maryland's broadcasting archive; includes many soundbites.

Old Time Radio Scripts - Simplyscripts.com's page of scripts of old radio programs