Hey dan, good one buddy, I almost fell off my chair when I read the words "cheap-ish", "accommodations" and "Madrid" all in the same sentence
As the saying goes, "welcome to the jungle, we've got fun & games" but we don't have decent inexpensive rooms. That should be Madrid's new motto.
With the coming of the euro, the increasing popularity of Madrid to students and travellers and the general AMAZINGNESS of the city and Spain on the whole, expect to pay upwards of 50.000 pesetas/month for a room in a shared apartment (there are cheaper exceptions but they are scarce and go FAST
). So, I am not sure what you consider "cheap-ish" but this is the reality of it all. Decent, central & well communicated (metro, bus, etc.) apts. and rooms are very hard to come by these days so I wish you luck.
All I can do is direct you towards my new classifieds section at
www.multimadrid.com/classifieds (new ads for Dec. will be up by this Friday, Nov. 23rd), as well as my accommodations hunting resource page at
www.multimadrid.com/mm_interactive/links/apts.htm 
Even my accommodations offered section of the classifieds is a bit slim this month, as if the situation were not bad enough
Saludos & Suerte,
jer...
- rent or buy a cell phone from me for your stay in spain, more info at 
- already have a cell phone, get a spanish SIM card for it at 
