Excellent topic Ken!!
Well, Martina appeared on Baywatch, Early Edition, and General Hospital and most recently Sesame Street!
Martina, along with Brooks & Dunn and several other country stars appeared on The Simpsons.
Paul, George & Ringo (separately) all appeared on the Simpsons.
Smashing Pumpkins, Peter Frampton and many others also appeared on the show. (I figured you woulda listed these Ken!)
Ray Charles appeared on Wings, and was also a recurring character on The Nanny.
Clint Black appeared on Wings.
Coolio appeared on The Nanny.
Steve Lawrence appeared on The Nanny, both as himself with Edie, and as Fran's dad.
Lisa Loeb appeared on The Nanny.
Brian Setzer appeared on The Nanny.
Sebastian Bach is now a recurring character on Gilmore Girls.
Bonnie Bramlett was a character for a short time on Roseanne, and David Crosby appeared in one episode as her husband.
Blues Traveler appeared in an episode of Roseanne, where John Popper was their old friend.
Sonny Bono appeared on Golden Girls.
London Wainwright III made three appearances on MASH as Captain Spaulding. (Character name was probably because Hawkeye was a big Groucho fan, and that was his most famous character)
Sammy Davis Jr made a most famous appearance on All in the Family.
Anthrax and Ed "Kookie" Byrnes appeared together on Married With Children.
Madonna was on an episode of Will and Grace (surprised Lora missed this one!!).
The Beach Boys appeared on Full House.
Tommy Page appeared on Full House. (Do I actually know that??)
Janet Jackson was a regular on Good Times and Different Strokes.
Michelle Phillips played on Beverly Hills 90210.
On a CLASSIC episode of Married With Children was Peter Noone, Mark Lindsay, Richie Havens, John Sebastian, Robbie Krieger and Spencer Davis.
And Ken, Marcia's other celeb kiss on Brady Bunch was Desi Arnez Jr (Dino, Desi and Billy)!