Analog Insydes is a Mathematica toolbox for symbolic analysis of analog electronic circuits. This project provides a set of free add-ons to Analog Insydes, including a Java front-end and a native netlister for Cadence's Analog Design Environment (ADE).
JPhysChem - a mathematical modeling toolbox designed to provide an abstract layer and a comprehensive graphical front-end for general model building and specific modeling and data processing in the field of mass spectrometry and physical chemistry.
NecJGui is an antennas design tool, interface for Numerical Electromagnetic Code. It allows easily making NEC input files, and viewing them in 3D. It also contains a version of the simulator, so it's complete IDE for full-wave EM simulation.