I second wolf359 - you'll want to go 720 x 480 (1:1 pixel ratio). If your target audience is US, I'd go 30 fps to avoid 3:2 pulldown artifacts, which is really a shame since 24 fps is a more intuitive frame rate for animating.

As an aside, I'm looking forward to creating my first blu-ray disc at 1080p; talk about render times going through the roof!