SouthWest has announced a new way to try to pry more $ out of travelers pockets. It is misleadingly called "early-bird check-in". You don't get to board any sooner, you just get the alleged privilege to "check-in" with them before some others.
It is a solution looking for a problem.
I think it is about $10 USD each way.
http://www.southwest.com/flight/early-bird-faq.html