ManualsLib - Just enter the keywords in the search field and find what you are looking for!
Manuzoid - Repository that includes user manuals for various products
ManualAgent - Manuals and guides
ESI - ESI is a huge database containing equipment schematics, service manuals, and electronic components that you can explore online.
Manula - Manula is an online software for creating user manuals.
Stonly - Create interactive step-by-step guides