I run one of those sites, and use the answerbank as a reference. There's only one of me , but a lot more contributors. If you want speen The Answerbank will probably be your quickest reference, however as it has millions of contributors. The benefit of my site is that it's very up to date (2700 ads, 2100 songs of which all but 30 have samples and more than 1900 can be instantly downloaded) and provides sample / download links so you can be 100% sure that the song is the one you want.
http://www.songofthesalesman.co.uk/
It all started coz I couldnt find the music to a Guinness advert , which turned out to be the superb Burke's Law by Prince Buster (which you cant download , but can listen to here)
http://www.songofthesalesman.co.uk/ad.aspx?par tist=Prince%20Buster