The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Planing (2 members)
- Planning (2 members)
- Plugin (1 member)
- Plugins (9 members)
- Podcasts (2 members)
- Point Counter Point (1 member)
- Politics (4 members)
- Popups (1 member)
- Porting (1 member)
- Portraits (1 member)
- Posts written when drunk (3 members)
- Preservation (2 members)
- Printable WeRelate (4 members)
- Printing (1 member)
- Priorities (1 member)
- Production (1 member)
- Programming (109 members)
- Project Gutenberg (3 members)
- Project Management (1 member)
- Proofreading (3 members)
- Prototyping (1 member)
- Public diary (1 member)
- Publishers (1 member)
- Pubs (2 members)
- Punctuation (2 members)
- QR codes (2 members)
- QRpedia (2 members)
- Quakerism (2 members)
- Queralbs (1 member)
- Queries (1 member)
- Quiet (3 members)
- Quotation marks (1 member)
- Quotations (8 members)
- RMS (1 member)
- RSS (2 members)
- Radio (2 members)
- Rails Through the Bush (1 member)
- Railway (2 members)
- Railways (1 member)
- Rants (1 member)
- ReStructuredText (1 member)
- Reading (54 members)
- Recommendations (1 member)
- Recording (3 members)
- Redaction (1 member)
- Reddit (1 member)
- Redirecting (1 member)
- Releases (1 member)
- Renaming (1 member)
- Renovating (1 member)