One of the last minute gifts I made for my mother was a set of marble magnets. I know I'm a latecomer to this project but I have to agree with how easy and rewarding they are to do.
I made a copy of this picture of my brother, sister and I with my mom and her mother, father, and brother's family.
I used the marbles to trace around the different people in the picture and then cut them out. I glued the picture to the back of the marble with Aleene's Tacky Glue, then glued a 1/2" magnet on with E6000. They're packaged in an Altoid's tin. You can find everything you need at Michael's. The marbles are in the floral section packaged in a little mesh bag, make sure you get the clear ones. Once home, I had to cull through them to find the ones that had the fewest flaws (like air bubbles) so I could get the clearest picture. If you don't want to do this then buy them in the scrapbooking section, you'll pay more but there won't be any wasted.