The ECLiPSe Constraint Logic Programming System is designed for solving combinatorial optimization problems, for the development of new constraint solver technology and their hybrids, and for the teaching of modelling, solving and search techniques.
JinnIde is a plugin that allows using Jinni Prolog, now also hosted here on this site (with open source license!), within the confines of an IDE integrated in JEdit.
The Prolog Expert System Shell (PESS) is a software that generates ES using basically two components: Knowledge Base, used by the ES to guide its decisions making, and Inference Machine, cable of collection the rules and generating new facts.