Hello,
Just from my expierences, I always find Northwest the cheapest (www.nwa.com). This is mostly because there are only 4 airlines from my airport: Northwest, Midwest, Contential, or American. Northwest is always the cheapest. However, if you do have a Southwest from your area, i strongly hear thats the best.
If jetblue runs out of your airport, they are incredibly reasonable. However, you can't get them on expedia or anything. You need to go right to their site jetblue.com