ManualsLib - Just enter the keywords in the search field and find what you are looking for!
ManualAgent - Manuals and guides
Manuzoid - Repository that includes user manuals for various products
Dozuki - Dozuki is a web-based tool for creating and distributing step-by-step documentation.
Manula - Manula is an online software for creating user manuals.
Stonly - Create interactive step-by-step guides