GLOOP is Liquid Object Oriented Particles. libGLOOP render implicit surfaces from a set of "meta-points". Uses include: modeling liquids, volume rendering, computerized silly putty. Based on code by Brian Sharp
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.