http://www.commandlinefu.com/commands/view/5427/get-your-external-ip-address

http://whatismyip.com

With 'curl':

curl ifconfig.me

or

curl ipinfo.io/ip

Using the 'lynx' text web browser:

lynx --dump http://www.whatismyip.com/ | grep -o '[0-9].*\.[0-9].*\.[0-9].*\.[0-9].*' -m1

or

elinks --dump http://www.whatismyip.com/ | grep -o '[0-9].*\.[0-9].*\.[0-9].*\.[0-9].*' -m1