My two GSDs get a half hour of chasing tennis balls every morning. It's the only way that Jody (my 4-1/2 year old male) stays calm for the rest of the day.

A walk is just not enough for either one of them.

I live in Ohio and I hate cold weather, I should move huh?..lol
A couple of winters ago, I had my chocolate lab with us at the park, my wife and I went there to play in the snow. Yea, I know..just big kids. So we thought it would be fun to take the dog.
Well there was a bunch of kids sled riding, and Ramsey (we call'm Rambo) LOVES to pull things. He is probably one of the few labs who you can "catch" on a sleeve and hold him up in the air, I digress. So kids always hate running back to the top of the hill, and Ramsey LOVES kids and pulling, so we asked the kids if they wanted a ride back to the top of the hill. The kids would slide down, Ramsey chasing them the entire way, sometimes knocking them off thier sleds licking thier faces off. Then I had the kids hold the leash and I'd call my dog to me, He'd run them right back up to the top of the hill. He kept this up for about an hour or so. He slept for the next two days, I'm not kidding, he barely wanted to go outside for a break.
But it was a lot of fun, the kids loved and my dog got some excersise and some social time.