This is a handy tip for saving some harddrive space (in my case, about 90MB) by removing orphaned Address Book photos.

First, you need to enable the Debug menu in Address Book. Quit Address Book, launch Terminal and paste this in (hit Enter if it doesn't automatically submit this command -- you probably won't see any feedback; just a new line):

 defaults write com.apple.addressbook ABShowDebugMenu -bool YES

Next, launch Address Book and navigate to the Debug menu. Click the "Remove orphaned images" item:

This will create a folder on your desktop called Orphaned Images full of type-less files. If you want to preview or Quicklook these images, you'll need to add a .jpg extension, which can be done easily enough with a file renaming utility like NameMangler or NameChanger.

In my spot tests, I found that the orphaned images were often duplicates of images in existing cards -- and that had been orphaned when I ran the "Look for Duplicates..." command and merge the duplicate cards that happened to have photos associated with them. In other words, you should be able to safely delete this folder.