Does depend on your intended projector or means of display. If you are using something capable of displaying HD TV then I would suggest resizing to 1920x1080 pixels, ie max 1080 pixels vertically or 1920 pixels horizontally, whichever gives the smaller picture, and save as JPEG at max quality. Seems to work great.
Interesting to note your occasional appearance on this forum, Samir.
I take it you have bought yourself a magnificant 55" Plasma or LCD display capable of true HD, right?