Hola Scott.
As the others have suggested, I will also say that MadridInsider, Welcome to Madrid, Madrid Flatmate and Room Madrid are all very welcome alternatives to the "Centros de Informaci�n" that will charge you a small fortune (about 250 Euros

), give you a list of mostly already rented apts. and then boot ya out the door.
The 4 services/agencies mentioned above all charge a flat fee and considering they all do the same job and have pretty much the same database of flats, I would recommend you go with the least expensive ones.
Since you speak Spanish I would recommend you give the search a go on your own first.
Unfortunately, finding a room from abroad is not easy so you may have to arrive, stay at a hostel for a few days and look hard for a room.
If you can't find your own place and need help, current fees for placing you in a room:
� Welcome to Madrid = 50 Euros or 16.66% of the first month's rent.
� Madrid Insider = 50 Euros.
� Madrid Flatmate = 68+ Euros.
� Room Madrid = 100 Euros
Like I said, go with the cheapest service since they are all pretty much the same.
Saludos,
jer...