Same was happening me on the way to the meet last Thursday. Started after i disconnected my battery. Was fine then on the way home and been grand since. My first thought was the MAF as Andy said.
Hold on, do the simple things first, check the tension and condition of the belt, don't go looking for pulley's. The squeal of a loose or worn belt, has nothing to do with the idle speed,
had a similar problem in another car and it was the throttle actuator ......ie the idle control valve.......was full of gunk. as far as i know its a little piston type thingy that lets small ammounts of air in on idle.....open to correction or a better explanation
as above
get a can of carb cleaner and wash out the throttle body but dont get near the MAF....
cheapest option first
then possibly the idle speed control valve....
not sure the maf will affect the idle speed in this way