Builder Xcessory PRO
GUI Builder for Motif targeted at mission critical applications. [Commercial]
Motif Programming/Reference Manuals Volume 6A/6B
The definitive O'Reilly Motif reference guides. Completely updated for Motif 2.1 and available for free download in various formats.
Motif Widgets in Motion
Three Motif widgets to display scientific data as dynamic plot.
Open Motif Everywhere
ICS's Open Motif built from the official Open Group sources. Precompiled binaries available on all popular Linux environments and FreeBSD.
Xlt widget set
The LessTif/Motif Extension library, is a set of widgets that make programming with the Motif API easier as it adds a set of frequently used tools, mostly authored by Rick Scott.