From what I've read, the best companion for a rabbit is another rabbit of the opposite gender, but neutered (unless you want lots of rabbits!).
Why is it miserable? If it looks a bit hacked off at being cooped up a lot, would giving it a bigger hutch/bigger run (fox proofed, of course) make it happier?
Or, have you considered allowing it into the house? I had a housetrained rabbit as a kid, he was awesome, more like a rabbit shaped dog. He liked the theme tune to The Bill, and hated Phil Collins.
Letting it loose is obviously a no-no, domestic rabbits aren't likely to survive in the wild for very long. Perhaps you could learn to live with your bunny's disapproval?