There is no page I'm aware of which collect Commons documentation and attempts to impose on it any kind of structure. This is a weak attempt to do so.
For an index of everything ever, see Commons:Editor's index to Commons.
Linked from Help:Contents
- Commons:Sandbox (for experimenting)
- Commons:First steps
- Getting Started
- Upload of files
- Good practice hints
Software helpful for Wikimedia Commons:
- Commons:Media help
- Commons:Software and tutorials for editing media files
- Commons:Tools tools for making work in Commons easier