2000 Chrysler Sebring • 80,000 miles

My car is not giving off heat. I changed the thermostat but when I turn the heat on I only get a brief (maybe 5 sec) of warm air then it cools. What are some other things I need to check. It is a 2000 chrysler sebring jx convertible. The fluids have all been topped off. It is too cold to be driving without heat so i'm willing to check anything.
Thank you
January 7, 2013.

Make sure both heater core hoses are getting hot. If they don't, flush the heater core. Also, check the blend air door to make sure it is working properly. It is a vent door that allows air to pass over the heater core. If it isn't opening or closing properly, you won't get heat. Finally, make sure the engine is running at a normal operating temp.