Got a car sittin' 'round, clutterin' up your driveway? Love the idea of handing over the keys to strangers? RelayRides, a recent beneficiary of some Google Ventures cash, has just brought its peer-to-peer car-sharing service to the San Francisco Bay Area. Already available in Boston, the service is sort of a "social bikes-meets-Zip Car." The idea is to let customers rent privately owned (and in some cases, leased) vehicles by the hour: owners receive sixty-five percent of the rental fee, and they're protected by a million dollar insuran