Oxford Music Online (Includes: Grove Music Online, The Oxford Dictionary of Music, and The Oxford Companion to Music)
Naxos includes CDs available for live streaming via the Internet
Alexander Street Press includes video streaming channels as well as audio streaming channels. This link lets you search them all!
Catalogs for recorded sound & video collections
Library of Congress Recorded Sound Reference Center
British Library Sound Archive Catalogue
Televised Opera and Musical Comedy Database
National Jukebox The Library of Congress presents the National Jukebox, which makes historical sound recordings available to the public free of charge. The Jukebox includes recordings from the extraordinary collections of the Library of Congress Packard Campus for Audio Visual Conservation and other contributing libraries and archives.
Live Music Archive is a community committed to providing the highest quality live concerts in a lossless, downloadable format.
Grooveshark Excellent source for popular music. Allows users to send links to individual tracks and customized playlists via email to other users. The person sending the links, and creating the playlists, must have a (free for now) account, but the recipients do not have to be members.
Websites of interest