Thule and Yak racks' cradles hold the top and seat tube simultaneously to minimize sway. They also make tray models.

For people with SUVs, p/ups with shells, vans, the Thule 954 Revolver, Yakima Swingdaddy and Softride Parallelogram are very convenient if you take a lot of trips because you can open your tailgate (or Suburban swing-out doors) without having to remove the bikes. No biggy for one bike to take off and put back on, but if you take 3-4, this feature is very nice.