hey Evert.
they advertise just not all of them do so in english.
as Juliette said,
www.in-madrid.com has a great classifieds section with many rooms offered.
check out
http://madrid.loquo.com as Nanny recommended, they have TONS of room rental and apt. share ads.
"The Broadsheet" (
http://www.tbs.com.es ) also has english language classifieds. the madrid section is
HERE but it is new so there is not much there right now.
see also the up-and-coming MAPMADRID classifieds
HERE
ok, there is a GREAT "pisos compartidos" section of "segundamano" at
http://inmobiliaria.segundamano.es/subseccion.cfm?categ...subcategoria_id=6300 . the madrid page is directly
HERE it is in spanish but with a spanish-english dictionary you should be able to muddle your way through.
also, if you have questions or do not understand something, you have us here to help so just post on this thread and we will clarify

i am with Juliette here, it is tough to get anything good while still abroad. get a temp place (for example through Madrid Insider (see link from Juliette above) and then look for more permanent digs when you get here.
saludos,
jer...