Open Source Digg (Social Publishing)

1. Blinkk – Blinkk is an application which combine digg, del.icio.us, and forum into a platform. View screenshot here.
2. Vote up/down Package for Drupal – A plugin for Drupal CMS which can create a voting system which similar with digg.
3. PHPDug – An open source digg-clone which support templates and has a very clean interface. It has several extra features such as automatically add stories from RSS feeds and multilingual support. View demo here.
4. Vote It Up for Wordpress – It is a Wordpress plugin to create the voting system. It support the latest Wordpress 2.5.
5. Upwarded – Simple digg-clone application. But unfortunately i can’t found much information about it.
6. Last but not least, Pligg – The most powerful digg-clone application which support templates and plugins. There are a lot of Pligg users, so i believe you can easily get support by the community.

http://www.techsnack.net/free-open-source-digg-clone-download

Top 5 open source Wiki engines

Top 5 open source Wiki engines versi benh.org:

1. MediaWiki
   www.mediawiki.org
   
2. TWiki
   www.twiki.org
3. PmWiki
   www.pmwiki.org
4. DokuWiki
   www.dokuwiki.org
5. MoinMoinWiki
   www.moinmo.in

selain itu anda juga bisa mencoba wiki engine yang lainnya:

• PhpWiki
• TiwiKiwi
• DekiWiki
• Xwiki
• FlexWiki
• OpenWiki
• Kwiki
• Very Quick Wiki
• TiddlyWiki