gNewSense is a free-software-only distro based off Ubuntu. They do not include anything restricted by legal issues like patents, etc.
I like the philosophical idea behind it, but it still needs time and work. I heard Canonical is going to discontinue gobuntu (their free-software-only variant) and merge it with gNewSense. That should be interesting.
On a side note, the BLAG distro has discovered that there's non-free drivers and tidbits in the unmodified kernel and has removed them in their distro.