Just saw an interesting site
https://relayrides.comBasically, if your car is sitting unused most of the time, you can post it online for 'rent' hourly or weekly. Relay Rides provides $1 Million dollars of insurance coverage.
Or, if you need a car for just a few hours a week, there may be someone down the block from you looking to rent their car to you at either hourly or daily rates.
Seems pretty cool no?
Not always going to beat rental car rates, but as a possible alternative to buying a 2nd car - and it can definitely be more convenient than renting if there's someone in your neighborhood with a car that you like!