Small project that can be hosted on a free Appharbor instance that makes it possible for computers to report their IP address. Why ? Because my dyndns account expired and it was more fun to build a custom thing than register a new domain. The back end is based on my new favorite .net project: Nancy. To get started simply create database tables based on the db.sql script and put a user name and password into the web.config. There's a ruby script included on github with a example client the one I run from a cronjob to keep track of the IP of my home computer.
For a even simpler client you could just use Curl.