(Update 2 09-30-2020) Webhooks — The Definitive Guide 
(Update 03-21-2019) Add the Power of Webhooks to Your App with Okta’s System Log (Joël Franusic at Okta).
I heard webhooks from Zapier the first. Below is an good article written by the folks at Zapier.
What are the webhooks? (Zapier)
Was trying to follow the tutorial from the above
requestbin works like described (encountered a few 500 errors, but mostly working)
It seems I could not open the hurl.it link from runscope community page.
My interest in webhooks is also inspired by this little JS program I wrote a long time ago. And this was rekindled recently due to the atomist-sdm (GitHub) (node.JS based SDM, automation, quick start here).