I drive a 2007 Dodge Caliber (even though it's only barely 2007 now, I've had it for a year). It's the perfect size for me, though fitting 3 seats in the back has been a bit of a challenge, I think I've figured it out. Right now I have a RF radian behind the driver's seat for DS, and a RF Britax Boulevard behind the passenger side for DD. We'll add another Radian to the mix sometime in June, in anticipation of #3's arrival (they'll be riding in the Boulevard though).
DH drives a 4-door Jeep Wrangler (also a 2007, this is the first and likely the *only* time we'll ever both be driving new vehicles at the same time), and DD also rides in a RF Britax Boulevard in there (also behind the passenger), with DS in a Turbo Booster. The kids don't ride in there often, and the seats are usually not installed so that DH won't have to worry about them when he takes the top off (risk of theft). Since the Boulevard is so easy to install though, it's not a problem to take it in and out
My mom (only other person the kids ride with) drives a 2005 Grand Caravan, DD rides in a RF Britax Boulevard (driver side, middle row), and DS uses a turbo booster (usually passenger side, middle row, but sometimes he wants to sit in the "way back")