Good stuff for any compost bin. Pablo_NH uses it directly in his garden.

Yup. The litter is pretty urine soaked usually. I assume that you also have spent hay in there (you are feeding Timothy hay, right?...) Hay and poop are probably great, but I dunno about spent litter.

I use wood pellets for litter- they expand into fine sawdust. They're as good or better than any of the other litters I've tried and at about $6 for a 40# bag- you can't beat it. I throw them into an outdoor pile or directly on beds as a mulch.

I should add- you can dispose of the poop by throwing it directly into beds or on the lawn without vermicomposting. Just keep adding to beds and it breaks down in place. I turned my whole garden into an outdoor massive vermicompost operation using mostly rabbit box stuff, shredded leaves, and used coffee grounds.

ditto what pablo said. My neighbor donates about 6 large garbage bags of bunny litter (hay, compressed paper pellet bedding, poop, shreds of vegetables) a month to our HOA flower beds. I have found since she started donating the stuff that the squirrels will not dig around in the beds for tulip bulbs if they have to go through a layer of the bunny urine scent. A nice additional benefit, above and beyond the fertilizing effect.