Review on hook.io by Brian Potter

I like that it lets me use any language or framework to write my own hooks, but also that they have built in support for many languages/frameworks (Python, NodeJS). It's easy enough to get started with if you're just looking at writing your first few hooks - there are some great examples included. The documentation could be improved. They should include more information about how to do things outside their API spec itself. We've been using this service to communicate between our applications without having to rely upon an external messaging system.