Several computer hardware and software manufacturers, including AMD, Hewlett-Packard, IBM, Microsoft and Sun, have gotten together and created a chip that will be built into computers that will, for all intents and purposes, broadcast a unique identifier that anyone will be able to read when you access the Internet.
http://www.msnbc.msn.com/ID/10441443
http://www.msnbc.msn.com/ID/10441443