| sly | GNU Lilypond Document |
| smdf | Surface Magic Design |
| smf | OpenOffice Math Formula |
| smht | Sealed MHT Document |
| smlx | Steel Markup Language Document |
| smm | Ami Pro Macro |
| smpl | Megahedron 3D Object |
| smst | Adobe Soundbooth Score Toolkit Document |
| smu | Simple MUsical Score Document |
| smus | Simple MUsical Score Document |
| smz | SMath Studio Compressed Document |
| snapdoc | Ashampoo Snap Document |
| snp | Microsoft Access Report SnapShot |
| snt | VX Show-n-Tell Slideshow |
| soap | Simple Object Access Protocol Message |
| sp | LTspice Netlist Data |
| spar | Spartan Document |
| spartan | Spartan Document |
| spc | LTspice Netlist Data |
| spdf | Sealed PDF Document |
| spect | Spectacles Document |
| spl | FutureSplash Animator Document |
| spot | Sealed PowerPoint Template |
| spotm | Sealed PowerPoint 2007 Template without Macros |
| spotx | Sealed PowerPoint 2007 Template |
| sppt | Sealed PowerPoint Presentation |
| spptm | Sealed PowerPoint 2007 Presentation without Macros |
| spptx | Sealed PowerPoint 2007 Presentation |
| sprt | Sprintometer Document |
| sprz | Sprintometer Document |
| spw | SigmaPlot Worksheet |
| srb | Corel WordPerfect Scrap Book |
| srtf | Sealed Rich Text Format Document |
| sru | Search/Retrieve via URL Response Format Data |
| ssi | HTML Document with SSI |