How do I find out what my external IP address is?

Question

My computers are sitting behind a router/firewall. How do I programmatically find out what my external IP address is. I can use http://www.whatsmyip.org/ for ad-hoc queries,

Answer 1

whatismyip.com or ipchicken.com are very easy to parse.

If you have a webhost or vps you can also determine it, without fear of it randomly going down leaving you stuck.