InterNIC

The Internet Network Information Center is a public registration database that lets users look up information on known IP addresses and Web addresses. It can be found here.

If you're on this page, you probably followed the link from Uplink. In that game, InterNIC is the least secure site on the Web, arguably making it a Game Breaker, although without access to such an easy-to-hack system, the game becomes Unwinnable By Mistake.

Pro-Tip: Don't try to hack InterNIC in real life. Not only is it illegal, but their servers are, in reality, notoriously well-defended. The more you know.