What are best websites for finding inexpensive airline roundtrip flights within Continental US. I live in ATL, so where do I begin?

It depends on where you want to go. Delta has the most flights out of Atlanta. Southwest has a number of flights as well. You can check out http://www.southwest.com./ Also check out http://www.orbitz.com./

Inexpensive airline is not on the big search sites. If you want a low cost seat then you look on the low cost Airlines directly.

Be warned the low cost seat has extra FEES for EVERYTHING.

https://www.flyfrontier.com/

https://www.southwest.com/

https://www.spirit.com/Default.aspx

These are the lower cost Airlines.

You can find low fares on the other Airlines too depends where and when you want to go.

There is no absolutely cheapest place to look for flights TO EVERYWHERE.

You do not need to use the same Airline in both directions. You do not need to take the same route in both directions. Up to you to look around.

The big search sites look for the FASTEST connection not the absolute cheapest you could possibly get.

Delta and American Airlines have the most flights. Helps if your flight should be delayed for some reason. They have more ways to get you there than the smaller Airlines.

READ THE DETAILS of getting a refund or Credit if you want to change your plans BEFORE YOU PURCHASE.. CHEAP SEAT is usually NO REFUND.