The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Rosie O'Gradys (2 members)
- Rotation (1 member)
- Roundhouse (1 member)
- Routing (1 member)
- Rowan Atkinson (1 member)
- Rsync (1 member)
- Rsync.net (0 members)
- SFTP (1 member)
- SGI 1600SW (1 member)
- SQL (4 members)
- STV (1 member)
- San Francisco (1 member)
- Satish Kumar (1 member)
- Saving (1 member)
- Saw horses (1 member)
- Saw stools (1 member)
- Sawdust (1 member)
- Sawing (3 members)
- Scanning (1 member)
- Scenery (1 member)
- Scheduling (1 member)
- Schema (1 member)
- Scotland (2 members)
- Scott Hanselman (1 member)
- Scripts (3 members)
- Searching (1 member)
- Selecting (1 member)
- SemanticForms (2 members)
- SemanticMediaWiki (1 member)
- Semantic MediaWiki (6 members)
- Semantic web (1 member)
- Sessions (1 member)
- Sewing (1 member)
- Sharpening (1 member)
- Shimano (1 member)
- Shipping (2 members)
- Ships (1 member)
- Silas Marner (1 member)
- Silence (1 member)
- Simplicity (1 member)
- Skinning (1 member)
- Slate (1 member)
- Slideshows (1 member)
- Slowing down (1 member)
- Snopes (1 member)
- Social media (1 member)
- Social networking (8 members)
- Societies (1 member)
- Soetsu Yanagi (1 member)
- Software (12 members)