Advertise where the sun don't shine: Ads are everywhere: toilet stalls, t-shirts, blimps, the Super Bowl halftime show, some yokel's forehead. Now Carrie McLaren of Stay Free! is stepping into the fray, offering advertising space on her colon. (Current bid is $22.50.) She writes: " Though invisible to the average eye, my colon will be viewed by an affluent audience of medical professionals. Overpriced pharmaceuticals, diuretics, and Frito-Lay products are a natural fit, but keep in mind that doctors enjoy a wide array of luxury products, too." Talk about niche advertising...