The next tip comes to us courtesy of Jason, Roger, Peter, Austin, Eli, Lance, and the rest of the Tekzilla audience. If you're rocking the OS X, but want or need thumbnail views in a folder, just follow these simple steps.
1. Open up a folder and select the icon view button at the top.
2. Right click (2 button mouse) or hold down the ctrl key and mouse (single button mouse) and click inside the folder and go to "Show View Options".
3. Increase icon size by dragging the little bar.
4. Click on the button that says "Use as Defaults" (Leopard) or click the button of the dialog window that says "All Windows" (Tiger) if you want to change all your folders this way.
Remember this only changes the view in the folder in icon mode only. If you switch to text and icon, you'll have to redo the steps and you wont be able to change icon sizes beyond the 2 offered. The steps will differ slightly between Tiger and Leopard.