The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Blogs-2 (0 members)
- Boats (1 member)
- Bookbinding (3 members)
- Bookkeeping plugin (3 members)
- Bookplate (1 member)
- Bookpresses (1 member)
- Books (27 members)
- Books in my collection (0 members)
- Boredom (3 members)
- Boring (1 member)
- Boring posts (1 member)
- Box (2 members)
- Boxes (1 member)
- Brad Pettitt (1 member)
- Brain Bag (1 member)
- Brewster Kahle (1 member)
- Bricklaying (1 member)
- Brindabellas (1 member)
- Broodiness (1 member)
- Bugs (4 members)
- Building (2 members)
- Bus stops (1 member)
- By the Ionian Sea (1 member)
- C.F. Barker Archives (1 member)
- CLI (1 member)
- CSV (2 members)
- Cafes (0 members)
- Cafés (8 members)
- Calendar (1 member)
- Calendars (1 member)
- Camping (1 member)
- Canberra (21 members)
- Captains Lane (1 member)
- Cargo (0 members)
- Carnival (1 member)
- Carrington Street (2 members)
- Cars (3 members)
- Cartography (1 member)
- Casio (1 member)
- Catalogues (1 member)
- Cataloguing (2 members)
- Categories (33 members)
- Categorisation (1 member)
- Cats (0 members)
- Causes (1 member)
- Centenary Building (1 member)
- Changes (1 member)
- Chicago Manual of Style (1 member)
- Chickens (3 members)
- Childhood (1 member)