The GoldenRatio is
It is often called "phi" or "tau", depending on which side of the pond you are on. Note that 1/phi = phi-1, And there's this really nice series to o with integral powers of phi.
A rectangle that has sides in the GoldenRatio was in the era before print and TV felt to be more pleasing to the eye than other ratios. The studies, however, generally compared 1:1 with 1:phi and 1:2, and people generally preferred the intermediate ratio. Later studies show that people can't really choose between 100:150, 100:155, 1:160, 1:165 and 1:170. The page at http://plus.maths.org/issue22/features/golden/ says a lot more about this.
Far more information available at Wikipedia
and any Google search will turn up more than you can read in a year.
I find that 1:sqrt(2) is pleasing, simply because I am accustomed to metric-sized paper. But when putting a JFrame on the screen, I always centre it horizontally and move it up the screen vertically by the golden ratio.
JFrame f = new MyJFrame();
// initialize the content of f
f.pack();
Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
f.setLocation((d.width-f.getWidth())/2,
(d.height-f.getHeight()) * (1000-618) / 1000);
Phi is also the ratio of all voters to "No" voters, and of "No" voters to "Yes" voters in the recent Dutch referendum on the proposed EU Constitutional Treaty.
More pleasing, in the same sense that different musical modes instill different emotions.