When you fire up a VM in Azure and don’t give it an external IP, you can still configure it to have access to the internet.

If you do so, it’s not immediately obvious on which IP that box appears to originate to the outside world.

curl http://ip4.canihazip.com

A great lifesaver, which returns the IP you made the request from in the body of the returned HTML page.

Update

It would appear by October than canihazip are having issues, so this no longer works, instead I would suggest using the following:-

curl ifconfig.co