Project URL : http://sourceforge.net/projects/ktechlab/

KTechlab is a development and simulation environment for microcontrollers
and electronic circuits.

KTechlab consists of several well-integrated components:
A circuit simulator, capable of simulating logic, linear devices and some
nonlinear devices.
* Integration with gpsim, allowing PICs to be simulated in circuit.
* A schematic editor, which provides a rich real-time feedback of the
simulation.
* A flowchart editor, allowing PIC programs to be constructed visually.
* MicroBASIC; a BASIC-like compiler for PICs, written as a companion program
to KTechlab.
* An embedded Kate part, which provides a powerful editor for PIC programs.
* Integrated assembler and disassembler via gpasm and gpdasm.

Project URL : http://gpsim.sourceforge.net/gpsim.html

gpsim is a simulator for Microchip (TM) PIC (TM) microcontrollers.
It supports most devices in Microchip's 12-bit, 14bit, and 16-bit
core families. In addition, gpsim supports dynamically loadable
modules such as LED's, LCD's, resistors, etc. to extend the simulation
environment beyond the PIC.

Project URL : http://sourceforge.net/projects/gspiceui

GspiceUI is listed among the Fedora Electronic Lab (FEL) packages.

GNU Spice GUI is intended to provide a GUI to freely available
Spice electronic cicuit simulators eg.GnuCAP, Ng-Spice.
It uses gNetList to convert schematic files to net list files
and gWave to display simulation results.
gSchem is used as the schematic generation/viewing tool.

Project URL : http://qucs.sourceforge.net/

Qucs is a circuit simulator with graphical user interface.  The
software aims to support all kinds of circuit simulation types,
e.g. DC, AC, S-parameter and harmonic balance analysis.

Project URL : http://savannah.nongnu.org/projects/simulavr/

A simulator for microcontrollers from Atmel's AVR series.

gEDA — набор программного обеспечения для проектирования электронных устройств (САПР), распространяемый по лицензии GPL. Включает в себя инструменты для редактирования электрических схем, симуляции цифровых и аналоговых схем, трассировки печатных плат и подготовки к производству. Проект изначально ориентирован на UNIX-совместимые платформы, хотя некоторые программы, входящие в его состав, в настоящее время портированы под ОС Windows.