Check out this experimental music discovery engine, upon which I stumbled by pure chance. I think it's a great idea:

a) you start by selecting a mood (or a dance beat) on a cross chart,
b) select the musical genres you wish to hear,
c) choose the musical era (!) in which you wish to hear songs (if you wish to discover past hits, this is it!)

You results are presented using a link chart featuring full songs, according to your search criteria. I haven't been through the whole experience, but I think the songs are also classified by tempo, so one song flows to the other just as if it was mixed by a DJ. The interface is still very basic, but serves the experience well.

If you wish to purchase the songs, one click takes you to Amazon, ITunes, or Ebay. It's a fantastic idea, and a great tool to discover new musical horizons. I think it's now a matter of minutes before some big company calls this guy and he becomes insta-millionaire.

Visit Musicovery now, and you'll be able to say you were there in the golden days.