I just noticed today that you can drag your iPhoto thumbnails directly to applications in the Dock. I've been exporting my images and then opening them in Photoshop, but now I can just drag them right to the Photoshop icon in the Dock.
[Editor's note: I'd been dragging the thumbnails to my desktop to export, but I'd never thought to try dragging them directly to the application icon in the dock. Neat trick!]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020718073403639