Localtunnel allows you to easily share a web service on your local development machine without messing with DNS and firewall settings.
Localtunnel will assign you a unique publicly accessible url that will proxy all requests to your locally running webserver.
Install Localtunnel globally (requires NodeJS) to make it accessible anywhere:
npm install -g localtunnel
Start a webserver on some local port (eg http://localhost:8000) and use the command line interface to request a tunnel to your local server:
lt --port 8000
You will receive a url, for example https://gqgh.localtunnel.me, that you can share with anyone for as long as your local instance of lt remains active. Any requests will be routed to your local service at the specified port.
See the github page and wiki for information on clients in other languages and the full API for the tunnel proxy.