First of all -
there already is a thread for music recommendations.
Second - why do you want to discover new pop music? Only a few of the good artists are on the top lists, and the radios don't seem to give a damn about them. Looking for pop music on the top lists will keep you from making a lot of new music discoveries. But if you really want to, try
Spotify, the ultimate music streaming and discovery application. There is a free version, too.