I have people come to my house and pick up my rabbit waste. They will put it around plants and trees in the fall and winter as a mulch, and compost it in the summer or dig it in to the gardens. My waste contains hay, poop, wood pellet litter, and the remnants from shredded phone books.
When I made a garden last year, I put cardboard over the grass (to kill it), then some leaves and lots of rabbit waste. Then covered the whole thing with a good layer of high quality dirt. The garden was very fertile and would grow mushrooms in the shady parts.
I'm going to try and make a small garden at my new place as well, and will probably use a similar technique.
Any stray poops not in the litter box, I put in a bucket for myself. I mix it into the soil I put potted plants in. Works wonderfully.
-Dawn