I just tried to open the websites based on the list of 50+ clones of digg. Most of them are not available anymore. The following list contains only the valid digg clones.

http://www.blinklist.com/
http://www.bringr.com/
http://www.business-planet.net/
http://www.care2.com/

http://www.dotnetkicks.com/
http://www.dzone.com/links/index.html
http://www.indianpad.com/
http://mootion.com/
http://www.motorpulse.com/
http://www.mp3rama.com/
http://www.beta.netscape.com/
http://www.newsgarbage.com/
http://www.newsvine.com/
http://www.oks.ph/
http://www.phetchit.com/ - based on wordpress, you can add your own links and posts without having an user
http://reddit.com/
http://sportsflip.com/
http://reddit.com/ - well known social bookmarking site
http://sportsflip.com/
http://www.shoutwire.com/
http://tutorialism.com/
http://upwarded.com/
http://videobomb.com/
http://www.videosift.com/
http://wink.com/
http://www.wobblog.com/
http://www.thelosthub.com/
http://www.grupl.com/links/best/
http://www.youtubedigg.com/
http://www.television2u.com/
http://www.karaoke2u.com/
http://www.scifidigg.com/
http://www.babes-daily.com/

http://motherapproves.net/

Most of te websites are based on pligg, a free open source php script, having the same features as digg. Some other websites are based on wordpress. Drupal can be used as well to create a Digg clone. Check how to create a digg like website, based on Drupal.