Back in September, I posted on HDTV viewing distance, screen height and it's become a very popular bit of search engine fly paper. Here are four more that provide pertinent information:
Carlton Bale, 1080p Does Matter - Here's When (Screen Size vs. Viewing Distance vs. Resolution). Link: carltonbale.com.
Matt Burns (pointing at the above, but adding some helpful comments), 1080p charted: Viewing distance to screen size. Link: engadgetHD.com.
Carlton Bale, Home Theater Seating Distances: Field-of-View vs. Resolution. Link: carltonbale.com.
Carlton Bales, Home Theater Calculator. Link: carltonbale.com. --Dennis