chris,
i applaud your desire to gain a greater undertanding and appreciation of the popular songs that have served as a foundation for much of jazz improvisation. i'd like to encourage you to seek out versions of these tunes that include vocals, rather than instrumentals. trumpeter kenny dorham reportedly said: "I always learn the words to a song. It helps me play the melody." you might try doing a search using the composer's name and look for collections of their songs. cole porter, irving berlin, george and ira gershwin, and other great composers wrote many of the tunes we now consider jazz standards. these collections might not contain the original versions of these songs (many were written in the 20's, 30's, and 40's), but they're pretty close and often less jazzy. if you really want to hear some original versions, check out fred astaire's recordings from the thirties. yes, that fred astaire! believe it or not, astaire was considered a faithful interpreter of american popular song, and he introduced quite a few standards to the public, including the way you look tonight, a fine romance, and let's call the whole thing off. otherwise, i think the ella fitzgerald songbook series already mentioned is a great way to become familiar with this part of the rich heritage of jazz. good luck and good listening!