ISETL - Interactive SET Language, distant SETL variant widely used in discrete mathematics: downloads on lower 2/3 of page, for DOS, Mac OS, Windows; source code available.
ISETLW - Interactive SET Language for Windows 95/98/Me/NT/2000/XP: downloads, documentation, bugs, sample problems.
Other SETL Sources and Documentation - Offers sources, documentation and references to programming language SETL.
SETL2 - SET Language 2, close relative of SETL, has some clumsy support for closures, an experimental (broken) object system, and redefines integer division to mean something different than in SETL: 3/2 yields 1.5 in SETL, but only 1 in SETL2.
SETL Documentation - SET Language: mathematical programming language closely resembling the language of sets and functions used by Mathematicians. Lets users define sets, then define functions and binary operations on the sets: reference documentation for the library of built-in operations.
Slim - General-purpose programming language resembling SETL, its close relative, more like SETL cousin than a child, since it shares common heritage, but is independently designed: innovative type model, object oriented, smaller, public domain.