There are several good screen reviews over at
www.projectorcentral.com - but not entirely comprehensive. Like other things, there is just to many screens out there to accurately test and measure them all.
Usually what you want is a screen that matches your room and typically some of the most reliable quality comes from fixed screens that hang on your wall like a picture - a very secure picture. They have rigid frames that the screen material snaps onto and you should get one with a velvet like black surround frame several inches wide to absorb any light that spills over the edge of the screen.
But, there is also pull down screens, motorized screens, and tab-tensioned motorized screens... oh, and rear projection.
Other considerations are the size of your screen and how much gain you want. Gain usually affects the viewing angle though. A 1.0 gain screen will reflect back basically exactly what you throw at it and should have a fairly wide viewing angle. A 2.0 gain screen will reflect more light back into a narrowed area which makes the image appear brighter. This may affect the viewing angle a great deal and from a single viewing position you may see the image appear darker towards one edge or another because of viewing angle differences.
The color of the screen and the material can not only affect how bright the image appears, but how dark the shadows are and the apparent contrast levels. A gray screen may help a particularly low contrast projector, but for most projectors these days gray screens aren't mandatory.
What is, and always will be mandatory is being able to make your room pitch black. If you can do that, even a white wall will look pretty good.
