For people who get a little bored of the original Mac icons used in applications Elite By Design has created a new icon set which I thought you guys might enjoy. If you are familiar with the iPhone icons, with the glass bezel and rounded corners, theses are in a similar style. In the pack there are two sets, black and white and 128px x 128px and 64px x 64px.
They are really nice, and can be used for replacing the default icon set. He also includes the PSD file which can be used to make your own icons. I would recommend changing the images size in Photoshop to 512px x 512px since this is the largest size which is used by your Mac if you are on Leopard. You also get better quality when used in Quicklook for example. You can download the whole pack from Deviant Art.
To change and icon, simply Get Info for any application and then drag the png onto the little icon in the top left of Get Info. To change it back simply press delete on the icon in Get Info.