stereo calculator
Here's a little application that you can use to calculate how far apart your (real or virtual) cameras should be to generate a given amount of parallax.
You have to enter:
a) distance from the camera to the closest object (maximum negative parallax)
b) distance to the screen plane (zero parallax)
c) distance to the farthest object (maximum positive parallax)
e) the camera's horizontal field of view (in degrees)
f) width of your final image.
It doesn't matter what units you use, as long as they are consistent; 'camera units' would normally be in inches, and 'screen units' would normally be in pixels.
The calculator returns positive, negative and total parallax. Because the calculator assumes parallel cameras (not toed-in), your images will be offset from each other, so it also tells you the amount, and how far you will have to manually slide them to correctly set your screen plane.
Eventually I'll get around to adding lens focal length as an alternative to camera field of view.
OS X only for now, XP eventually.