A few guys cycled through the Yardbirds who made it big later. Not singers, but both Page and Beck in addition to Clapton.This one as well...
In college my first couple years, seemed any time, day or night, someone on the dorm floor was playing either Beck's "Blow by Blow" album, or "Frampton Comes Alive."
So Peter Frampton is the next question. What band did he play in before hitting big as a solo artist?