If you are searching for cheap flights to Atlanta, you'll get the best deals if you fly anytime from September to October. A roundtrip ticket from San Francisco, for example, would just cost $255.39 at Frontier Airlines and $275 at AirTran Airways, United Airlines, US Airways, Continental Airlines, and American Airlines. After October, roundtrip flights (same sample route) would already cost a minimum of around $300 inclusive of fees at the same airlines mentioned. Altogether though, US Airways seems to offer the best flight rates to Atlanta, next to Frontier Airlines.
Below is a list of Atlanta airports that you might find useful: