HD Moore (creator of metasploit) had a talk about doing something like this. He scanned all of IPv4 hitting common TCP and UDP ports, and collected data about the services running.
He found a lot of cool stuff. For instance, there are apparently 7 Windows NT 3.5.1 boxes with SNMP open sitting on the internet. And about 300 IIS servers that give out the same session ID cookie when you log on.
That's actually quite interesting! Thanks for the link, it's always very awesome to hear speeches by the people "behind the magic."
Also, I thought this quote on the page you linked was pretty humorous: "[HD Moore] is the Chief Architect of Metasploit, a popular video game designed to simulate network attacks against a fictitious globally connected network dubbed “the internet”.
He found a lot of cool stuff. For instance, there are apparently 7 Windows NT 3.5.1 boxes with SNMP open sitting on the internet. And about 300 IIS servers that give out the same session ID cookie when you log on.
The visualizations are also really nice. The talk is here: http://www.irongeek.com/i.php?page=videos/derbycon2/1-1-2-hd...