I am looking for an inexpensive hostal, around 30 euros per night for a double room in the central area of Madrid. If it had a little charm that would be ideal, but clean is the most important. Anybody know one?

Try the recent thread "Hostels in Madrid" for 25€-and-under lodging ideas in Madrid.
In that thread, I list 4 hostels in your price range and other users list more. That should get you started but there aren't many places where you can get a private bedroom so cheap. Hostels in Madrid are pretty famous for being clean but you won't find many with charm. Most inexpensive lodgings are quite simple in furnishings and ammenities. Those which do have some charm are always more expensive.
Saludos, MadridMan