Car rental companies are eliminating flexible one way car rental returns. Major car rental companies like Avis, Hertz and National used to treat a Metro area as one car rental facility. With corporate and leisure rates, customers used to be able to rent from one metro area and return to another - i.e., rent at SFO and return at SJO. As recent as January 2009, I rented a car from National at LAX and returned the car at SNA without penalty.
Since March of 2009, I began to realize the major car rental companies are charging their customers for returning to a different car rental facility. I was looking to rent a car from Hertz or National at Burbank airport and returning the car to LAX and noticed extra charges for dropping the car off at a different location. adds a drop off charge with unlimited miles while Hertz charges a standard daily rental rate plus $0.30 per mile.
There are however exceptions on the east coast. Due to the competitive nature of the one way rentals in the greater New York area, you can still get good rates when you rent from NYC and return it to New Jersey/Newark. I have also rented from downtown Philadelphia and returned the car to PHL without any penalties or extra mileage charge.
I recommend you read the fine print of the car rental quote before you commit to the contract. Flexible return policies are out the window in this tough economy.