Draper, Stewart, and DaLite all make screens which can do this and are designed for this. I use a Draper Ultimate Access V screen, which uses two trap doors to fully hide the screen when it is retracted. I like it a lot.
Size is going to be dependent on your viewing distance and the actual room size to house the screen.
For a projector, it depends on your budget, but the Epson 8500UB and the Panasonic AE4000U are class leaders right now.