These new traps I'm seeing are pretty neat, especially the one that electrocutes the mice. It musn't take much since it's only using small batteries.
Someone a while back posted this homemade trap:
Take a bucket, run a wire across the top and through a beverage can, put a ramp leading up to where the wire attaches to the one side of the bucket, smear some bait on top of the can. Apparently the mice crawl across the wire tite rope style and when they step onto the top of the can it flips them into the bucket. An option is to fill with enough water to drown them.
I may give this one a try today. I'm getting sick and tired of finding mouse turds all over the hoods of my tractors, but with an open sided pole barn... it may be a losing battle.