Best way to rent a car one-way?

You can get a train. See http://www.amtrak.com/servlet/ContentServer?pagena...

for fares. I did a random day on October and found fares for as little as $48, up to about $75.

I don't know the ground transportation situation at either end, but you may need to get a taxi between the train and airport (and vice versa). In any case, it will be less expensive that renting a car and being hit with the drop off fee.

There are two stations in Philadelphia. The first is closer to the airport:

2955 Market Street

30th Street Station

Philadelphia, PA 19104

and

2900 North Broad Street

Broad St. and Glenwood Avenue

Philadelphia, PA 19132

There is one station in Pittsburgh:

1100 Liberty Avenue

Pittsburgh, PA 15222

There aren't any ways to squeeze out of set fees. You will just have to suck it up and pay the fee. Your only other options are to change your departure flight so you'll be departing from the same airport you arrived at, or drop the car back off in Philly and take some other form of transportation to Pittsburgh (i.e. bus). Everyone who drops their rental car off in a different location has to pay the fee, there isn't any reason you should be exempt from the fee that everyone else has to pay for the same thing.

Well there are car rental companies also who provide the facility to pick and drop the car from different locations, that will be suitable for you either. As you want only one way travel so you can go contact them or check on their website. There are a number of companies for that among one is http://www.usacarsrental.com/ so go contact them and ask for your situation. They will surely tell you the solution.

Go to http://travelcatcher.com/index.php?p=1_4_Car-Hire#...

Great car hire comparison site and some do not charge extra for different location drop off