I've updated Oak, the Rails blogging engine I'm working on, to support webmentions.

Both sending and receiving are supported at this time, though manually.

Sending is manual so that you can control if/when you actually want to send a ping.

Processing of a received mention is manual so that we don't become a vector for DDoS, nor post spam all over our own sites. Received mentions live in a queue, and you can process them as you wish.