The Phiculator is a great little application, that you can download as a flash file as well (don’t know but I love applications that come as flash files). It calculates ? (phi), the golden ratio. To put things into a design perspective, if you’re trying to make a website that is 850px wide, it gives you the size of the column that splits this 850px line in an aesthetically pleasing way. So your main column would be 525px in that case. Also I really love James Mellers’s site as well.