The Frugal Flugel recommends Zipcar! Zipcars can be found in cities across the USA and are a great option when you need a car for only a few hours. There is a $25 one-time application fee to join and an annual fee of $50, but then you get dirt-cheap hourly rates. In Chicago a Zipcar is $9 per hour; the same car in New York City is only $10 per hour.
The Frugal Flugel recommends REGIONAL AIRPORTS! For big savings, fly a low cost airline to a small regional airport near your destination. For example, instead of flying directly to Philadelphia International, try taking Spirit Airlines to Atlantic City International, just one hour away.