Personally I think http://www.reddit.com/r/Bitcoin/comments/1mavh9/trustless_bitcoin_bounty_for_sha1_sha256_etc/ http://www.reddit.com/r/Bitcoin/comments/1mavh9

Personally I think http://www.reddit.com/r/Bitcoin/comments/1mavh9/trustless_bitcoin_bounty_for_sha1_sha256_etc/ http://www.reddit.com/r/Bitcoin/comments/1mavh9/trustless_bi... is pretty cool. I am not aware of other systems which can do that.