Thoughtful, detailed coverage of the Mac, iPhone, and iPad, plus the best-selling Take Control ebooks.
 
Find Photos in iPhoto in the Finder

Looking for the file associated with a photo in iPhoto? In iPhoto, to view a photo's file in the Finder, Control-click it and choose Show File from the contextual menu that appears. You can then drag the file's icon into an Open dialog to upload it to a photo-sharing service, for instance, but whatever you do, don't move or rename that file!

Visit iPhoto '09: Visual QuickStart Guide

From Adam C. Engst