The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Music (1 member)
- MySQL (4 members)
- NaBloPoMo (3 members)
- Namespaces (1 member)
- National Library of Australia (1 member)
- Nature (2 members)
- Neal Stephenson (1 member)
- Necromancy (1 member)
- News (3 members)
- Newspapers (2 members)
- Nikon D60 (1 member)
- Ninthfloor.org (1 member)
- Nomenclature (1 member)
- Non-fiction (3 members)
- Noongarpedia (1 member)
- Not good enough (1 member)
- Notes (1 member)
- Nyunga (1 member)
- O'Connor Community Garden (1 member)
- OCD (1 member)
- ODK (1 member)
- ORM (2 members)
- Offsite (0 members)
- One thing well (1 member)
- Ontology (4 members)
- OpenLibrary (1 member)
- OpenRosa (1 member)
- OpenStreetMap (6 members)
- Open Data Kit (1 member)
- Open Source (3 members)
- Open content (65 members)
- Open source (1 member)
- Open standards (1 member)
- Optimism (1 member)
- Order (1 member)
- Organisation (1 member)
- Organising (2 members)
- OwnCloud (1 member)
- Oxford University Press (1 member)
- P. G. Wodehouse (1 member)
- PDF (1 member)
- PEAR (1 member)
- PHP (9 members)
- PLUG (1 member)
- PVA glue (1 member)
- Pages using deprecated source tags (5 members)
- Pages with script errors (21 members)
- Pages with syntax highlighting errors (4 members)
- Painting (1 member)
- Paperwork (1 member)