Depending on the space in which you intend to use this, you may be able to get away with using the classic 'white painted wall.'
This is an inexpensive screen; it rarely ripples, and is relatively easy to clean and maintain. In a worst case sort of scenario, you grab a roller and refresh the surface.
This, of course, works on the assumption that you have a reasonably large, blank area of wall someplace 'useful' for the screen purposes, that isn't obstructed by speakers, monitors, pictures, cats, or whatever.
If these conditions are true, then you've got $1500 for a projector. Then things become much more interesting...
I've been fairly happy with my Panasonic PT-LC75u, which tops out at 1024x768 (non-HD.) People have offered good words about the Panasonic PT-L500, which does offer true HD, 16x9, et cetera.
Take a look over at
www.projectorcentral.com and look around.
Leo Kerr
Lkerr1@alumni.umbc.edu