Wondering what physical path an email message (from a friend or some spammer) had followed before reaching your inbox ? Try the Email graphic traceroute service.
You copy-paste your email headers in the Email Routemap web interface and the service draws the path of your email message on Google maps.
For the above screenshot, we used a test mail sent via yahoogroups.com.The orange icon (destination) denotes the location of Yahoo! Mail servers while the green pin indicates the origin or the location from where that email message was sent.
Another very interesting Google Maps mashup is Google Maps Traceroute - type in any IP address and the service will show the exact physical location of that IP on Google Maps.