Cyme International - Offer software for various analyses, design, parameter calculation and distribution.
Designer's Guide Consulting - Provides verification and simulation services to companies involved in integrated circuit design. Includes information resource about modeling, theory and analysis, as well as a discussion forum.
Hbfree - Free command line RF/microwave harmonic balance circuit simulator, for analog nonlinear circuits simulation with diode and MESFET nonlinear elements.
Infolytica - Offer electromagnetics design software for both low and high frequency applications. Products include MagNet, ElecNet and FullWave.
Schematica - Windows software for design of active filters and linear circuit simulation