Depending on the amount of light control you have, my $150 DIY screen made of Wilsonart, Designer White (D354-60 ) laminate is proving to give fabulous results. I generally view with blinds over my one window that block all but ambient light and with a dimmer set just high enough to provide safe navigation in the room. Pretty dark, but not so you can't easily navigate or see to pick up your food or drink.

I've cranked up the lighting a ways too and it still performs wonderfully. The strength of your projector is, of course, also a big factor here.

If you are interested, here is an extremely informative thread (if you ignore his rant as he argues with a salesperson) that includes color and gain charts and very good directions on how to frame and mount it. Some photos of results too although I'm disappointed he used different scenes to display the different laminate colors.

Laminate Projector Screens

Lots of other info on Laminate and Paint for screens if you Google. Purchased screens are, of course, a much easier choice.

With great power comes Awesome irresponsibility.