Our friends at clickertraining.com have an entire series of challenging, interactive dog games and toys to challenge your dog!  Most require your participation though.

and/or all the other fine products from one of my favorite stores: SITSTAY.COM

The Talk-to-Me Cosmic Treat Ball has so many features, bells and whistles, your dog is sure to love it! You can record a message for your dog in your voice and it will play the message back along with motion activated lights and sound. You can fill it with treats and reward your dog as it plays with the ball by dropping treats out of the holes! Large 6" treat ball is for dogs over 30 lbs. SMALL available -click here.
 

The Buster FoodCube and the Buster MiniCube are ingenious toys for mental stimulation of your dog and a fun way for the dog to utilize excess energy in a natural way!
 

The Bouncy Bone chew toy is a nice alternative to straight rawhide or nylon chew bones. The experience lasts longer and offers more variety by combining a rubber chew ball, "Gnawhide" rings, and a nylon "bone." Click her to see it in action - it is at the end of the Tug a Jug video.
 

Irresistible new interactive toy to keep your dog engaged.

Blow long-lasting bubbles for pets to chase and pop. Bubbles dry in the air, and land on the ground intact, waiting to be attacked by dogs and cats alike. Pets really love chasing and bursting these bubbles! Economical and fantastic fun. Comes in peach flavor (non-toxic of course).
 

A great interactive toy for all breeds and sizes. Any dog that likes to herd anything will love you for it! There is a removable plug so, if you like, you can insert your dog's kibble and have it work for its food!  Great stress reliever for hyper dogs at J-B Wholesale Pet Supplies
 

Similar to the Jolly Balls above but with cutouts and an interior ball that causes erratic motion when the ball is tossed.  Available in both 6 inch (8.00) and 8 inch (10.00) sizes.  Go to Jolly Teaser Balls and scroll down to the bottom of the page.
 

Kong makes a number of products for powerful chewers and other pets! Other Kong products
 

For bone lovers and extreme chewers! Stuff a treat in the ends and watch the fun begin. For most large and medium dogs. Made from the extra durable black rubber stands up to the most tenacious chewer.
 

World’s Strongest Rubber Dog Toy. Three sizes are available to satisfy large, tenacious power chewers.
 

Made big and strong of X-tra tough nylon for POWER CHEWERS!