I'm kind of impressed by Spirit Airlines' new carry-on baggage fee.

And it looks like Congress is too: http://www.businessweek.com/news/2010-04-13/spirit-s-carry-on-bag-fees-draws-senate-bill-to-ban-practice.html

Carrying a bag onto a Spirit flight will cost passengers $45 at the gate, or $30 if paid in advance, starting in August

Even AirAsia and Ryanair haven't thought of that one...but I'm guessing they'll try now.