Check the coolant level as mentioned. If its low, and its a 2.7, check the water pump for leaks immediately. In fact, dont drive it until you know the water pump is good. Drive the car for at least 20 minutes, and come back and feel the hoses. Upper and lower radiator hoses should be hot, and both heater hoses should be hot.
If you have any cold hoses, the thermostat is sticking open. If all hoses are hot, then the problem is in the heating system. It could either be the blend door actuator, that opens/closes the hot/cold air door, or the heater core is plugged. Next step would be to remove the actuator, and manually move the door to the hot position. If you still have no heat, replace the heater core.
If its a 3.5, with 110K miles, it would be a good time to replace the timing belt/water pump unless you know its been done already.
Last edited by Daytrepper; 12-21-2009 at 11:29 PM.