I had been looking for a simple way to create wallet size photos using 4 different photos per 4x6 print size that I can purchase for the same price as a normal photo.
I came across this website on a 2Peas post: Photility and I love it! It is so easy to use!
Download the Photosheet software (for free). Open Photosheet and select how many photo you want on the sheet and how big you want it. Then open your folder with your photos, grab your photo and drop it into the program. It leaves your original photo in place and when you have dropped all the photos you want just click "start" and it saves your creation in the folder you pulled the photos from. Then print using your favorite company.