Pi-Hole is a DNS sink server which blocks ads and malware based on the DNS resolution. It is light on resources and can be installed in Raspberry Pi. By default; it installs Lighttpd.
DokuWiki is a PHP based software for creating your own Wiki. There are alternatives such as TiddlyWiki , MediaWiki , and BookStack.
There are other documentation solutions such as MkDocs which looks great accompanied with Material Design theme.
“Learning How to Learn: Powerful mental tools to help you master tough subjects” is a crucial course(most popular MOOC) which teaches you the effective techniques of the process of learning.