I'll second the Yakima. I have one on my Protege5 (I've used it on other cars, too), and it's about as solid as a trunk rack can be. It is important to wipe the pads and the places on the car where they touch, or you'll get scratches for sure.
I also have a Yakima top rack on a Honda, and it feels a lot solider, as you'd expect. But the trunk-mount one cost $80 at REI, and the top rack, with all the accessories you have to buy, came to more than $500. Costs a lot in gas, too--at 75mph, I get about 34 without a rack, 26 with two bikes on top.