Girl Talk is huge right now. People are loving these mashups.
If you haven’t heard of Girl Talk, it is the musical project of one man who “produces mashup-style remixes, in which he uses often a dozen or more unauthorized samples from different songs to create a new song” (Wikipedia).
My friend recently turned me onto a fascinating site that visually shows which sample is being used during each part of the song. Definitely check it out: http://www.mashupbreakdown.com