Don't remember which forum I saw it on; it may have been Bushcraftusa.com or backpacking.net. One of the members made a small hammock for his dog, he hung the doggie hammock under his own hammock. This accomplishes a few things.
1: keeps the dog off the cold ground
2: keeps the dog close to you
3: offers the dog a bit of shelter from any bad weather that might roll in.