Lets face it, Leopard is great, but you mac may be long in the tooth. What to do? You can always stick some more memory in the machine. I know, times are tough and you don’t want to spend money. Believe it or not , the 3D dock in Leopard takes up bit of resources just to make it shiny. “We don’t need that”, you yell at me. Very well, this is how to get rid of it.

Open up terminal ( it’s in your application folder under utilities, you can also just type terminal in spotlight).
Enter this in the window:
defaults write com.apple.dock no-glass -boolean YES; killall Dock

The dock should close out and open up in 2D mode. There you have it, a short and sweet hack. If you ever want to change it back all you have to do is set the Boolean value to NO in that command.