Just found the BEST toy for my Yorkie. She spends hours playing with it and never tires of it. It's called a Hide a Squirrel and she looooooves it!
Here's a pic:
http://thepuppyshop.com/tn111.html
I found it at my local pet shop, but it's probably available elsewhere! If you buy it, you'll be glad you did. And no, I'm not a rep for the company, lol.