The SML.NET distribution includes a number of samples. Here are screenshots of some of them:
The winning entry from the ICFP'00 programming competition, translated from Caml to SML by Stephen Weeks, tweaked for SML/NJ by John Reppy, and given a Windows Forms interface by Claudio Russo.
(Thanks to John and to Team PLClub for kindly letting us redistribute the code: Jerome Vouillon, Haruo Hosoya, Eijiro Sumii and Vladimir Gapeuyev).
An interpreter for an untyped, vaguely XQuery-like, language for querying XML documents. The interpreter is written in SML (using a lexer and parser generated by ml-lex and ml-yacc) and uses the .NET libraries to read and write XML files. The user-interface of the demo is an ASP.NET page (with code in C#) which calls into the SML.NET code to perform query evaluation.
John Conway's "Game of Life". Implemented in SML by Chris Reade and glued to a Windows Forms interface written in C# by Claudio