Avril Lavigne - Almost Never
Christina Aguilera - Besides from "Moves Like Jagger" rarely.
Kelly Clarkson - Currently Mr. Know It All a lot and her old hits sometimes.
Rihanna - All The Time and sometimes to much
Genuinely, outside of Moves Like Jagger ... not really ever. Once in a while - and I truly MEAN once in a while - a station might play Genie or Beautiful.