lazymention
lazymention is an open source service you can run on a Node.js server to send Webmentions from static sites. Its general purpose is to add dynamic building-block features to otherwise static websites.
Lazymention crawls submitted URLs for h-feed and h-entry markup, then does processing if it encounters any new content.
Currently it supports Webmention.
WebSub is planned for the future.
The source (and documentation) is on GitHub.