Just for posterity before anyone gets totally confused:
Mashup - a term used in the DJ community, popular also with podcasting audiences and creators, referring to the creative blending of two or more songs into a single track, such as an MP3 mix.
Mash-up - a term used to describe the growing Web 2.0 community of developers that create new applications derived of public APIs like those from Google, eBay, Flickr, and Technorati.
Good grief.