Steve Weller has a very nice tutorial along with an OmniGraffle template concerning the making of pixel-perfect icons for iPhone application toolbars up at his site.
Having gone through much the same thing myself using OmniGraffle to create icons and images and the like for Cocoa applications, it's very nice to see this sort of thing documented well.
Have a look-see for yourself, How to Draw Pixel-Perfect iPhone Toolbar Icons.
Excelsior!
