One page per platform. Each sets out how the system stores content, what it is built on, whether it is still maintained, and which parts of it have no equivalent anywhere else.
Pages are added as they are written, so this list grows. Where a platform is not covered yet the link will not be here.
Content management systems
WordPressPosts, pages and custom types
JoomlaArticles and nested categories
TYPO3Page tree, enterprise PHP
Tiki WikiWiki CMS groupware
Movable TypeOne of the earliest blogging platforms
ContentstackHeadless, API-first
DrupalEntity and field based
Concrete CMSIn-context editing
Kentico.NET CMS and DXP
Adobe CQNow Adobe Experience Manager
Static HTMLHand-built sites, no database
Forum software
IP.BoardForum software by Invision
vBulletinLong-running commercial forum software
MyBBOpen source forum software
Simple MachinesFree, open source, long established
Hosted and desktop builders
WixHosted, proprietary editor
SquarespaceHosted, template driven
BloggerGoogle’s hosted blogging platform
Google SitesGoogle’s hosted site builder
WebnodeHosted site builder
JimdoHosted site builder
WeeblyHosted builder, now Square
Serif WebPlusDiscontinued desktop builder
RapidWeaverDesktop site builder for Mac