Replied to a tweet by Toby Osbourn (Twitter)
I wrote and intro article on Webmention a while back for A List Apart: Webmentions: Enabling Better Communication on the Internet and Jason McIntosh just wrote Webmentions, Active and Passive which is solid.

From there, I’d take a look at the canonical Webmention page of the IndieWeb wiki which has a huge number of resources. Since it looks like you’re coming from a Ruby perspective, you might appreciate the Ruby page on the IndieWeb wiki which has some pre-existing resources which may cut back on your work and learning curve. Perhaps Jason Garber (@jgarber)might be a useful resource within the Ruby world?

If you’re using other platforms/languages, simply search the IndieWeb wiki for other details relating to Webmention. Have questions as you delve in? Just ask in the IndieWeb chat.