The Uptime Project is the arena for the hardcore enthusiasts to compete against each other by comparing their ... uptime. It is as simple as it sounds. The site holds records for different machines and, of course, their uptime.
The site has been running for over 3 years now. It hosts the uptime of over 2000 machines, but only 500 are online for most of the time. Their goal is to find the machine with the most uptime and the contest is opened to everyone. What you need to enter is simply one of their tools, which can be found on their website. Multiple platforms are supported, including various Linux distribution, Windows, Mac, Sun and I even saw an Android device in the rankings.
It is an amusing little project and I found the Windows application to be an easy way to get information about your systems uptime, without digging through command prompt.
Currently the record is held by a Sun server, running Solaris 2.6 (release date July 1997). If you have a machine which never stopped running for the last 5 years and a half you have a good chance of beating the current winner.
What is the longest time you had between reboots? Let us know by using the comment section below.