Dr.Explain - Dr.Explain software is a help file authoring tool.
ManualsLib - Just enter the keywords in the search field and find what you are looking for!
HelpSmith - HelpSmith is a help authoring tool to create CHM HTML help files, manuals, and PDF documents.
Manuzoid - Repository that includes user manuals for various products
Help & Manual - Help & Manual is a documentation authoring tool that allows you to create a single source text and convert it into a number of other target formats.
ManualAgent - Manuals and guides