Ikiwiki is a wiki compiler; it generates static web pages from a directory tree of plain text files, by default written in Markdown. In this respect it is similar to Jekyll, however Ikiwiki provides a CGI-script, which allows authentication with OpenID (and others), online editing of pages, viewing the (Markdown) source of pages, etc. thus enabling online collaboration.
Ikiwiki has good support for blogs and other aggregations, like todo lists, bug tracking, forums. On the other side it is sometimes criticized for its default web design
IndieWeb community members using ikiwiki to run their primary site (and potentially more).
Georg Lehner uses ikiwiki on several sites.
People running ikiwiki as a secondary site or on a subdomain: