You might think you've got some PowerPoint skills, but check out what Screenr user slhice of Ice Ltd. has created. With some graphics work that might impress even a veteran Photoshop user, she's assembled a great-looking iPhone template from scratch on a PowerPoint slide (she's working in PPT 2007 on Windows, but you can probably replicate her steps in PPT 2008). This could be very useful if you're giving a proof-of-concept presentation to a group, teaching an "iPhone 101" course, or running any other slide deck that needs some iPhone love.
We haven't tried to mimic the procedure in Keynote, but it sure would be fun. In the meantime, use slhice's method to wow the next group you lecture about the iPhone.