AMG: Vocal Music 
Overview of the genre, essay, key artists and albums, and recent releases.
http://allmusic.com/cg/amg.dll?p=amg&sql=F0VOCALAmerican Popular Song 
Message board and directories of singers, songwriters, movies, and shows.
http://www.americanpopularsong.com/
Craig's BigBands and BigNames 
Historic reviews and photos from performers of the 1940s, 50s, and 60s. Includes old time radio broadcast, quiz, and message board.
http://www.bigbandsandbignames.com/
Ian Whitcomb's Literary Corner 
Includes articles on Rudy Vallee, Duke Ellington, Irving Berlin, and the first crooners.
http://www.picklehead.com/ian/literary.htm
JD Hay's Crooners 
Library of songs in WAV format, including those by several pop artists and a 1950s collection.
http://www.angelfire.com/retro2/croonerjd/index.html
Parlor Songs 
Collection of popular and classical sheet music from the 1800's to the 1940's, cover art, audio samples, composer biographies, and articles on the history, styles, and themes.
http://parlorsongs.com/index.asp
Jukebox: American Popular Music in the 1930s 
Includes 40 audio files, with background and commentary.
http://xroads.virginia.edu/~UG03/Jukebox/front.html
Wikipedia: Melodic Music 
Defines "melodic" genre as the vocal-oriented popular American music style that came after big band music but before rock and roll, as exemplified by singers like Perry Como and Margaret Whiting.
http://en.wikipedia.org/wiki/Musical_genre#Melodic_music
Topix: Vocal 
News about vocal, collected from various sources on the web.
http://www.topix.com/rss/music/vocal.xml