PICsim is described as 'emulates a microcontroller PIC16F628/16F777/16F877A/18F452/18F4550/18F4620 and periferics such as USART and timers, the simulator architecture permit easy implementation of external elements in c language'. There are five alternatives to PICsim for Linux and Windows. The best alternative is Virtual Breadboard, which is free. Other great apps like PICsim are proteus VSM (Paid), SimulAVR (Free, Open Source), simavr (Free, Open Source) and Emulino (Free, Open Source).
It is a circuit simulator on a virtual breadboard. it supports virtual components like microcontrollers, TTL, graphical and alphanumerical LCDs and others in addition to virtual instruments and certainly the basic components (resistors, capacitors..).
The SimulAVR program is a simulator for the Atmel AVR family of microcontrollers. (ATtiny and ATmega) SimulAVR can be used either standalone or as a remote target for avr-gdb. There is a python- and TCL interface.