I found a Widget worthy of note. Widgets are little programs that can run on your Mac – OS X 10.4 and later. Screenshot Plus is a fantastic screen image grabbing tool that allows you to capture any element of your screen and save it to your desktop, your home folder or even open it in Photoshop. You can save images in many formats, but the default is PNG, which is fine by me.
If you've got Tiger, this one is worth a look.