Options below are listed in order from lowest to highest quality. I'd go with the most expensive, but also best quality, option 3a.
1,2.) If you want to send the projector Composite or S-Video, use the
Apple Mini-DVI to Video Adapter, MSRP $19. A fifty foot composite (yellow RCA) cable is $22
here, or 50' S-Video cable, $25
here +
here.
3, 3a.) If you want to send VGA, use the
Apple Mini-DVI to VGA adapter, MSRP $19. A 50' VGA cable, is $30
here. Delete the 50' VGA cable and add a [VGA to component adapter](active device) and
50' RGB snake.
4.) If you want to send DVI, use the
Apple Mini-DVI to DVI adapter, MSRP $19. A 32.5' DVI cable is $60
here (32' seems to be the max limit.)