I recently had a similar dilemma, although it was under stairs I was dealing with. I planned how I wanted it layed out, including drawers etc, I then bought 2 sheets of 8'x4' pine and cut all my doors from them. A router to finish off the edges and a few coats of varnish and I'm delighted with the results.
Personally speaking I'd go pine before MDF all day long...! :-)
Here's a link to a pic.
http://i112.photobucket.com/albums/n...ps0395b716.jpg