Standard ML.

Implementation.
libs.

Implementation.

http://www.standardml.org/: Implementations of Standard ML
http://www.polyml.org/: Poly/ML
http://www.smlnj.org/: Standard ML of New Jersey (SML/NJ)
http://www.itu.dk/people/sestoft/mosml.html: Moscow ML

libs.

http://mgtk.sourceforge.net/: GTK+ bindings.