Jet Blue flies to Houston. It is phenomenally cheap. here are the departure cities:
http://www.jetblueairways.com/images/dot.gif
Boston, Buffalo, Burlington, Charlotte, Chicago, New York, Pittsburgh, Portland,ME, Raleigh, Rochester, Richmond, Syracuse, Washington.

Flights start as low as $39, (hard to believe) but the earlier you book, the cheaper it is and they are a great airlines. Sadly, nothing from Miami.

Wow, thanks for that, someone may find it useful!!

Rachel x

There is also www.iflyswa.com which is Southwest Airlines and they are very reasonable, plus are notorious for specials.