During the year our son spent in speech therapy, we learned three easy/inexpensive ways to help strengthen his underdeveloped facial muscles. Although these are not technically AD's, they did wonders.
1. Taking a small sucker (like a dum-dum) and playing tag with it, having London use his tongue to try and chase it as the therapist moved it around. After it was done, the then got to suck on the sucker.
2. Milkshakes....what a perfect idea for a child who not only needed to strengthen his facial muscles, but also gain weight. You can make shakes at home too, just make sure they are thick enough that your child truly has to work at sucking to receive the mix.
3. Blowing bubbles into a cup. Get a see through plastic cup with a lip, and a straw. Fill it half way with water and let them blow away.......the harder the better.
This all sounds silly and fun......which it is for the child. But it works too!