Rod Roddy also did two cartoons. He was (what else?) a game show announcer in an episode of Garfield and Friends, and many know he was the voice of "Mike" in the Disney "House of Mouse" cartoons.
Bob Barker also lent a brief voice cameo in an ep. of Family Guy where Peter Griffin imagines himself on Survivor, and knocks over the set to reveal 3 contestants spinning the Big Wheel on TPIR.
Bud Collyer was the voice of Superman in the original Superman cartoons.
(as well as the radio series)
Gary Owens (who hosted The Gong Show and Letters to Laugh In) lent his voice to several cartoons, including Space Ghost, Blue Falcon, and Dirk Niblik (Square One)
Paul Lynde (not a host, but a frequent panelist) was the voice of Templeton in Charlottes Web, the Pumpkin in Journey to Oz (an obscure but great cartoon sequel to The Wizard of Oz), the villain in the gawdawful cartoon The Perils of Penelope Pitstop, and also Wendell T Wolf ("It's the wool-olf! It's the wool-olf")