Miraheze

Miraheze is a free, non-profit wiki hosting service that uses MediaWiki as its hosting engine, it provides any extension of your choice, including Extension:VisualEditor and Extension:Flow.

Extensions
Miraheze can download any extension of your wish and enable it on your wiki, some notable can be found on Wikimedia's git repository (the official MediaWiki git). To see extensions that are currently downloaded on Miraheze see their github.

Custom domains
If requested, Miraheze provides support for custom domains, but under domains some conditions.