I am currently working on a Java library which facilitates decentralized CoinJoin-ing using a BitcoinJ backend.
I applaud!
Current plan:
1. Implement peer discovery (perhaps using a DHT)
2. Fix error handling and enhance verification of transaction components
3. simplify, refactor, rename
4. post source code?
5. Make CoinJoin process more anonymous.
6. ALPHA release?
I think it would be good if you removed the "?" from number 4, no?
I don't have much time currently, but let me know if you need testers.