david grohl of foo fighters started as the drummer in nirvana. Has a good roll in the foo fighters (lead singer,guitarist) and also does drums for the queens of the stone age. Maybe some more in the future.
Some of the Italian producers (behind the likes of Black Box) also have a lot of credits. Queen would also be a fair shout - all but John Deacon had solo success and Roger Taylor produced Jimmy Nail's first hit "Love Don't Live Here Anymore" in 1986