We had quite a few, but since the announcement of the API 2.0 we're working on a new set of samples.

If you're interested in writing webhook handlers (for events or/and incoming messages) there is nothing new to learn: use http://postbin.org for debugging and from there it's mostly about the PHP itself and its frameworks.

If you're interested in using our HTTP API, we can send you some samples and perhaps collect some feedback. Please contact me: ev@mailgun.net