We've been really impressed with this winter sleeping bag from Snugpak. It certainly keeps you warm and is now my go-to sleeping bag for the colder months.
CONS:
Although it does pack down relatively small compared to some other four-season sleepings bags used with car camping, you can fit this one into your backpack, but it will take up a lot of room. If you want to go backpacking, look at some of the more expensive Snugpak sleeping bags.
