registry.scheme.org/filename-extension.scm

(id ".scm")
(stands-for "Scheme")
(description "Source code for any implementation or standard")

(id ".sps")
(stands-for "Scheme program source")
(description "R6RS program")

(id ".sls")
(stands-for "Scheme library source")
(description "R6RS (library ...) form")

(id ".sld")
(stands-for "Scheme library definition")
(description "R7RS (define-library ...) form")

(id ".rkt")
(stands-for "Racket")
(description "Racket source code with #lang at the top")

(id ".scr")
(stands-for "Scribe")
(description "Text document written using Scheme Scribe")

(id ".scrbl")
(stands-for "Scribble")
(description "Text document written using Scribble")

(id ".ss")
(stands-for "Scheme source")
(description "Equivalent to .scm")

(id ".sc")
(stands-for "Scheme")
(description "Equivalent to .scm [rare]")

(id ".sch")
(stands-for "Scheme")
(description "Equivalent to .scm [rare]")

(id ".sps7")
(stands-for "Scheme program source")
(description "R7RS program [rare]")

(id ".six")
(stands-for "Scheme infix")
(description "Scheme + infix lexical syntax [Gambit]")

(id ".spi")
(stands-for "Scheme package interface")
(description "ScmPkg package definition file")

(id ".stk")
(stands-for "STk")
(description "Scheme code written in the STk/STklos dialect")

(id ".ostk")
(stands-for "Object STk")
(description "Compiled STklos Scheme code")

(id ".brl")
(stands-for "Beautiful Report Language")
(description "Text document in BRL [Kawa]")

(id ".krl")
(stands-for "Kawa Report Language")
(description "Text document in KRL [Kawa]")