Lineage is the multisite management tool for the open source and Python-based Plone CMS.
Lineage 2.1 was released this week with improved Plone 5 compatibility as well as several bug fixes. Some of these improvements were made to @@lineageutils, specifically to add the current_childsite method and fix isChildSite to be called as a method on its view. This is a big usability enhancement for Plone developers who may have code that only works in a child site.
Initially developed by Six Feet Up, the free add-on allows website administrators to turn a folder within a Plone site into a new subsite in just a few clicks. Not only does it allow the site to have its own theme separate from the parent site, but it also allows each subsite to be controlled by a specific group of people, and allows the subsite to inherit content from the parent site. As a result, Lineage drastically simplifies the management of tens to hundreds of subsites.
Check out Lineage and Six Feet Up's involvement in its development.