The Arizona Republic covered the idea of carsharing services and noticed that Zipcar is available in Phoenix.
I belong to Zipcar, although it's not the most convenient service for me. I hope that perhaps it might spread in Phoenix to my neighborhood--my other option is to eventually move downtown where there's fewer daily services within walking distance but access to the cars would be easier. Zipcar has a partnership with ASU, so the cars are located downtown, in Tempe, and at one apartment complex in Scottsdale by ASU. I have to take the light rail to get a car and return home by bus, so a lot of the time it just makes more sense for me to take a cab or the bus to get places. I'm undecided on whether to renew my membership this fall, but for the $50 membership fee it might be worth it just to see how often I would use it in the next year. I do want to read the IPO papers to evaluate it for an investment.