Oscar Goodman gave the city another publicity boost this week when he appeared with David Brenner on the ultra-addictive Cash Cab. But we’ll remember this episode less for the money he won ($1,400) and more for the fact he didn’t know what a ShamWow is. We’ve got a way Oscar can make amends and help his beloved Mob Museum at the same time: Become a ShamWow spokesman. He’s already got experience, courtesy of Bombay, and hey, he must need something to help clean up after all those martini parties.