While most folks will recommend big SUV-type things, I gotta stick up for my little Acura Integra hatchback two-door. I live alone, drive alone most of the time, so I leave the back seats down all the time. I just remove the front wheel, put the back wheel into the hatch, roll it back as I lift the fork in, lay it down, put front wheel behind my seat or just in the remaining space in my car, and off i go. Tons of room for bags of gear/shoes/helmets/groceries, whatever.
I was pleasantly surprised that when my boyfriend left a bike up here that we could also put TWO bikes in. My frames (being smaller, but still a 50cm) would fit, upright, behind the seats. Again, take off the front wheel, fold the seats up and roll the back wheel in until it hits the other door. Turn fork, slide in front wheel, push seats back, and put the other (bigger) bike in the hatch section. I hate the thought of using racks - dirt, rain, theft, overhead crashes, rear-end crashes, etc. that I wouldn't do it any other way.

While it sounds complicated, it takes me literally 10 seconds to get my bike in or out. MUCH less time than folks with racks.