The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Legs (1 member)
- Lenovo (2 members)
- Libraries (7 members)
- LibraryThing (2 members)
- Libre (1 member)
- Lighting (1 member)
- Lightweight markup languages (2 members)
- Links (3 members)
- Linux (7 members)
- Linux-voice (0 members)
- Linux/ (0 members)
- Literature (2 members)
- Little Creatures (2 members)
- Living (2 members)
- Local history (1 member)
- Localisation (1 member)
- Log404 (1 member)
- Log entries (0 members)
- Logging (1 member)
- Logic (1 member)
- Logs (1 member)
- Luddism (1 member)
- MGA (1 member)
- MIME types (1 member)
- MacKennal Street (1 member)
- Mac OS (1 member)
- Mail (1 member)
- Making (7 members)
- Manifesto (2 members)
- Manton Reece (1 member)
- Mapping (2 members)
- Maps (2 members)
- Marco Arment (1 member)
- Markdown (2 members)
- Market Street (1 member)
- Markup (1 member)
- Marrion Zimmer Bradley (1 member)
- Marvin (1 member)
- Materials (1 member)
- Maximums (1 member)
- Mbox (1 member)
- MediaWiki (20 members)
- Meetings (4 members)
- Meetups (4 members)
- Melbourne and Mars (1 member)
- Menorca (1 member)
- Metadata (1 member)
- Methodologies (1 member)
- Microformats (1 member)
- Migrating (1 member)