Not sure how useful this trick is, or even if it will survive the next system update. (Mine is running the latest versions of OS X Tiger and iLife '05.)
I was working this morning on using iPhoto Buddy and our external FireWire hard drive so that all users on my machine could share the same iPhoto library. I set up an copy of my iPhoto library on our external drive using my account, then Fast User Switched over to my wife's account to see if she could view it, make changes, etc.
Before I switched her to the external library using iPhoto Buddy, however, I noticed that the library on the external drive was available to her using iPhoto library sharing! Sure enough, both her and my account had iPhoto sharing set up, and since iPhoto was still running in my account, it was sharing my library from the external hard drive to her account with the library on the local account. User ratings (0-5 stars) were preserved through sharing, as usual, although keywords were not.
The next time I want to move iPhoto pictures from one computer to the other, I'll definitely use iPhoto Buddy, the external drive, and iPhoto library sharing to simplify the process.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20051231120250490