In the past I have used Picnik.com to create collages. It is a process were I must first export photos from Aperture 3 to a JPEG file and then upload them into Picnik.com. Picnik.com has preset collage templates which you have some control over. I wanted to do something different yesterday for the New York State Fair collage I posted.
In looking for a better way to create that collage, I found a youTube video by Photographer Pete Thorne (see below) explaining how to use Aperture 3 and its book function to create multiple photo images. It took me less than five minutes after viewing the video to create the collage from yesterday. All done inside of Aperture 3. I had a lot of control over the size and placement of each photo. Something not available in Picnik.com. I could add text in hundreds of stylized fonts and place it over, above or next to photos or use an export plug-in to create bordering effects. I will be continuing to explore this tool.
This is not an ad for Aperture 3 but you might want to look at the features of the photo editing software you use. You might be surprised at what it can do. I know I was.