For those who have magnetic letters or other magnets, but have a stainless steel fridge to which no magnets stick, use the magnets on your washer/dryer, trash can, or oven, depending on if these things have exposed sides in a safe place in your house. (They work great there at my house.) [I happen to have a metal back door — perfect for this purpose. Also, while the refrigerator doors may not work for magnets, the sides usually do. — Ed.]
We also use a non-stick cookie tray for fridge magnets. They stick wonderfully. Then we can sit on the floor together and play "I Spy" with the contents of the cookie tray. Julian loves to identify the letters and pull them off the tray, and then put them back on to start again.