iPhoto 4 also gives you perhaps the weirdest and wildest way to share your photos online—and on your network: publish them as a .Mac slideshow.
When you send your photos out into the world as .Mac slides, other Mac OS X users can subscribe to your show, displaying your pictures as their screen saver—without having to manually download any files or launch a Web browser. (They do, of course, need an Internet connection.) In a minute or so, your latest photos can appear as full-screen slides on the Macintosh of a friend, family member, co-worker, or anyone else who knows your .Mac membership name.
Creating and viewing a .Mac slideshow requires Mac OS X 10.2 or later.
Note, too, that if your aim is to turn your photos into a screen saver only on your Mac (and not make them available to the world at large), you don’t need a .Mac account, and you don’t need to follow the steps below. Instead, use the Desktop button (page 226). It’s quicker and cheaper, and it doesn’t require an Internet connection.
Before any other Mac users can connect to your slideshow pictures, you have to make them available via your .Mac account. (If you don’t have a .Mac account, you’ll be prompted to sign up for one when you attempt to use the .Mac feature. See page 57.) Here are the steps for publishing your slideshow:
In iPhoto, select the photos you want to make available as screen saver slides.
If you don’t select any specific photos, iPhoto creates your .Mac ...