I'm splitting my time between Chicago and Raleigh lately, and it looks like I'll continue to do so for quite a while. This causes one minor inconvenience: my car doesn't fit in the overhead compartment on a CRJ. (For that matter, an anorexic gerbil won't fit in the overhead compartment on one of those things, but that's another issue.)
Chicago, however, is a major city with an extensive public transportation system (no snickering from natives, please). Chicago also has Zipcars, a by-the-hour car-rental cooperative, with six cars stationed less than four blocks from my house. Four blocks—800 m—seems to suburbanites like a very long walk to get a car, but actually, I'm lucky if I get to park my own car that close most days. So this is an improvement.
iGo, which costs a little less and works in partnership with the CTA, is another option. Unfortunately they don't have any cars within 1500 m of my house. Walking around the block to get the Zipcar suddenly seems more attractive. Walking eight blocks to get a car is less so.
Zipcars also has the advantage of national reach. Given how often I travel (especially to San Francisco), this has tremendous appeal.
Now if only Chicago had a puppy-rental service for those times when I miss Parker...