FastHelp - FastHelp is a Windows Help File Generator that produces online and offline documentation.
ManualsLib - Just enter the keywords in the search field and find what you are looking for!
StepShot - Make knowledge sharing more time-efficient!
Manuzoid - Repository that includes user manuals for various products
HelpNDoc - What is HelpNDoc ? Easy to use yet powerful help authoring environment which can generate various documentation formats from a single source.
ManualAgent - Manuals and guides