WordPress is Open Source blogging software that runs on PHP and MySQL. WordPress has an active support community that provides guides, themes, plug-ins and other resources.
Blogger.com is a hosted blogging service powered by Google. Users can quickly create accounts and begin blogging using a clean, easily navigable interface.
LiveJournal allows users to quickly create an online space centered around a private journal, a blog, a discussion forum or a social network
b2evolution is an Open Source blogging engine that runs on PHP/MySQL, and offers file and photo management, advanced skinning, multiple blogs support as well as detailed user permissions.
WeblogMatrix is an ever-expanding comparison area for weblog software and hosting sites. As there are more software options than can be listed on this page, CALPER recommends this site as a good springboard for learning about the many, many weblog programs available.
MediaWiki is a Open Source Wiki engine that was created originally to power Wikipedia. Supports multilingual use.
UniWakka is a light-weight, easy to use Unicode-based Wiki that can be configured to run on nearly all servers.
WikiPatterns is a hosted Wiki service that allows users to quickly create up and being using Wiki spaces.
SocialText is a Wiki hosting service with an emphasis on supporting professional collaboration.
PBWiki is a Wiki hosting service that provides allows users to create "free" (advertising supported) Wikis or choose to upgrade to a paid professional account with no advertising.