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,
http://ipecho.net/plain appears to be a
workable alternative, as whatismyip.com now requires membership for
their automated link. They very kindly appear to be
offering this service for free,
so please don't abuse it.