http://groups.google.com Google Groups. Read Usenet on the Web and create groups of your own.
http://www.isc.org/index.pl?/products/inn The InterNetNews Usenet server and reader.
http://slrn.sourceforge.net "s-lang read news"; the slrn newsreader.
http://knode.sourceforge.net KNode newsreader in Kontact and KDE.
http://pan.rebelbase.com The Pan newsreader for GNOME.
http://c2.com/cgi/wiki?WikiWikiWeb WikiWikiWeb, Ward Cunningham's original collaborative site.
http://c2.com/cgi/wiki?ChoosingaWiki Choosing a WikiEngine, with help from Ward Cunningham's assembled masses.
http://zwiki.org ZWiki, the Zope-based wiki engine included in SUSE Linux. Docs still in progress.
http://zopewiki.org/ZopeAndApache Getting Zope and Apache working together. Helpful when hosting ZWiki on Apache.
http://twiki.org Another popular Wiki engine.
http://en.wikipedia.org The Wikipedia home page, perhaps the best example of how wikis work.
http://www.list.org Home of the Mailman list manager.
http://www.greatcircle.com/majordomo The Majordomo list manager.
http://www.siliconexus.com/MajorCool The web interface for Majordomo.
http://www.irchelp.org The place to get help with Internet Relay Chat.
http://www.irc.org/links.html IRC clients, channels, networks, and bots. Find them here.
http://tldp.org/HOWTO/IRC The Linux IRC mini-HOWTO.
http://kopete.kde.org Kopete, the KDE instant messenger and IRC client.
http://www.jabber.org/user/userguide The Jabber user guide, for learning about this open-source IM protocol. Jabber.org also hosts a public IM server for you to connect with.
http://gabber.sourceforge.net The GNOME Jabber client.
http://xchat.org The Xchat home page.
http://www.licq.org LICQ, the mother of all Linux instant messengers.
http://gaim.sourceforge.net This IM client started as an AOL Instant Messenger (AIM) clone, but now supports most other IM networks as well.
http://www.gnomemeeting.org GnomeMeeting videoconferencing home page.