Nothing really polishes a podcast more than background music or theme music. In the music world, these music segments are referred to as intros and extros. While many enjoy streaming Internet Audio and recording songs they like over the Internet, these songs cannot legally be used in a podcast.

Podsafe music refers to music specifically for podcasters. The music is licensed in such a way that podcasters can purchase a license to include the music in a podcast without incurring additional fees or expenses. In order to use traditional music that is heard on the radio in a podcast, podcasters may have to pay royalties for each time the song is played. Some music files licensed under public domain or creative commons are exempt from royalties and these songs are available for use in a podcast, but generally when searching for music to include in a podcast it is probably best to stick with music that is specifically designated as "podsafe".

How and Where to Locate PodSafe Music - http://www.feedforall.com/how-to-locate-podsafe-music.htm