If I'm home and nearby I give Bailey bully sticks (especially
http://www.westbrookdog.com 's curly ones).
When I leave her alone for a while I leave a variety of entertaining toys that she loves.
She has a puppy kong which I fill with the kong stuff'n.
I just got her a busy buddy bone, which she LOVES, but it doesn't take her long to eat all the rawhide and the replacements are kind of pricey.
Busy Buddy Bouncy Bone - Dog.com
Her favorite is probably the busy buddy twist n' treat
Busy Buddy Twist n' Treat - Dog.com
And one of my favorites that Bailey also likes is the Talk to Me treatball, which records my voice and I usually just put her dry food in it, but you can use treats too
http://www.petco.com/product/108544/...t=OnSiteSearch
Oh, and of course a hide-a-squirrel. When I leave I also put little pieces of puppy cookies inside for her to smell/find.
Kyjen Hide-A-Toy Squirrel - Dog.com