There are 3 minimize effects in Mac OS X, out of which 2 are given as a standard choice. They are:
1. Scale effect (default), and
2. Genie effect
The third effect is hidden and can be enabled by means of a terminal command.
Without further ado, here it is:
"defaults write com.apple.dock mineffect suck" [Enter]
Try it out by double clicking on the title bar of any window or by clicking on the minimize button. The suck effect is one of the many ways to add a hint of customization to one's Macintosh.