Controlling Arduino over WAN

Hi all,
I was thinking about going a step further in Arduino programming and I was thinking of controlling an led over WAN (different networks) , not LAN. I just need some of you who know some already made projects over WAN or some tutorials on how to control an Arduino over wan to post these here please! I will really appreciate and thanks in advance!

http://lmgtfy.com/?q=Arduino+over+WAN