One of the really cool new features in iPhoto (part of iLife '06) is the ability to compare multiple photos at once in full screen mode (a feature brought to iPhoto from Aperture). Prior to now, comparing photos was possible, but only in the same window, and it wasn't as nice.

To do this, you first need to have the latest version of iPhoto. Once you have installed it, simply highlight the photos you would like to compare. They can either be several photos next to each other, or you can select several photos from anywhere in your iPhoto Library by holding down the Command key.

Once you have them selected, click on the full-screen button in the lower left-hand corner. It looks like this:

You will quckly enter into a full-screen preview mode with the selected photos on display side-by-side. At this point, you can change the photos that are on display. If you want to swap #2 with another photo from your iPhoto Library, simply select the #2 photo, then go to the top of the screen and select the new image to replace it with.

In the example below, I highlight 3 photos to compare. Once they are on display, I decide to replace the second photo with another one from my Library. Watch how easy it is to do: