Let me fix that last link: Wheel Mount Bike Rack - 3 Bikes
I bought a Yakima 3-bike trunk mount rack that seems to be really nice. 6 straps on this one, and it holds well. I've only done a test run, but it was at highway speed on a rough road, and it stayed tight with one heavy bike on it. Mine was $60, on sale from $90, at Dick's Sporting Goods.