I adore my 2001 Toyota RAV4. When I take out the back seats, I can fit a large VariKennel plus two large dogs in the back. Otherwise, they are just folded up for general use and I can fit three loose big dogs in the back with plenty of room. I've also gone camping in this and was able to lay out my sleeping back and sleep in the back, as did my 5'11" boyfriend at the time. Just scoot the front seats all the way up.
I got between 30-32 mpg on the highway the last time I took a roadtrip, and average about 24-27 mpg in the city. It's got a great turning radius, though I'm not terribly thrilled with it's handling abilities in the snow. I'm going to add some weighted sandbags and see if that helps any. Otherwise, that's about the only complaint I have.
I got mine for just over $15,000 with 48,000 miles on it. And it's Toyota, so you know it's going to last for freaking ever.