Music, of course, is a big part of what makes advertising, um sing. And we've come a long way from Alka Seltzers's pop-pop fizz fizz (which by the way is now hosting a contest to open source the famed jingle). Lots of mainstream commercial artists lend their songs to be used in TV ads and now you can buy a bunch of them on iTunes (iTunes link). The collection includes Chrstina Aguilera (Verizon), The Pussycat Dolls (Heineken) and more.
