Apple offers several methods of getting iPhoto, although it's worth noting up front that iPhoto is no longer a free download, as it was before iPhoto 4.
Ways to get iPhoto:
Look in your Applications folder. If you purchased your Mac since January 2006, iPhoto 6 may already be installed.
Buy a $79 copy of Apple's iLife '06, which is a CD/DVD package containing all five of Apple's digital hub applications: iPhoto 6, iMovie HD 6, iTunes 6, iDVD 6, GarageBand 3, and iWeb. Although these applications come free with new Macs, the iLife package is the only way for current owners of iPhoto, iMovie, iDVD, and GarageBand to get updates for those products. Visit www.apple.com/ilife/ for details.
Buy a new Mac, which will come with iPhoto pre-installed. Steve Jobs thanks you.
Rather than buy multiple copies of iLife '06, you can buy a $99 family pack that's licensed for up to five users.