Can you hear the heater working on full blast? If you can and nothing comes out it sounds like the air is being directed away from your vents - prolly a section of the duct has come away
or - I could be wrong - but if your temp guage needle doesnt go up to normal operating temp position then it could be as cheap and simple as a new thermostat - I'm not sure if a faulty therm would affect the actual output of heat
It doesnt sound like an expensive job to me
<img src='http://img.photobucket.com/albums/v629/BLACKBMW1/alssig.jpg' border='0' alt='user posted image' />
Thought for the day: "d'uh"