Another one is http://nullrefer.com, which seems to be quite stable and is used by some “chans”.
Usage:
http://www.nullrefer.com/?http://www.google.com
I think the best approach here would be a server-side plugin (instead of JS executed in browser) that adds the service as a prefix to all external URLs inside of .cooked posts. That way web crawlers would not leak referrer information to linked sites.