HTTrack - HTTrack is a free (GPL, libre/free software) and easy-to-use offline browser utility.
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
WebCopy - Cyotek WebCopy is a free tool for copying full or partial websites locally onto your harddisk for offline viewing.
Wiki.js - An open source, modern and powerful wiki app built on Node.js, Git, and Markdown.
SiteSucker - SiteSucker is a Macintosh application that automatically downloads Web sites from the Internet.
TiddlyWiki - a non-linear personal web notebook