circuit simulation

I would like to share some of the things which i feel may help you if yor are interested in electrical/electronics simulation etc...
KTechlab is an opensource software which can very nicely simulate a circuit. You can drag-drop components to make a circuit and can also use it to program PIC microcontrollers. available components include normal lump circuit elements and also electronic ones like BJTs, FETs, LCDs, RAM, Serial/Parallel bus, Flip-Flops, op-amp, 555, logic-gates and many other useful ones. It can also plot the probe values as in an oscilloscope. So check it out if u wanna see some cool circuit simulation.
Screenshots at http://ktechlab.org/wiki/index.php?title=Index:Screenshots

Also theres 'qucs' which is a more advanced . It has advance features which could check out yourself(as i dont know so much about electrical). However its features include a component library (find components by their no : brigdes, FETs etc) and AC/DC analysis, Transient analysis, S-Component Analysis and many more advanced things (eg u can add transmission-line as a component in ur circuit analysis and consider its effects!)
From the site : " Qucs, briefly for Quite Universal Circuit Simulator, is a circuit simulator with graphical user interface (GUI). The software aims to support all kinds of circuit simulation types, e.g. DC, AC, S-parameter, Harmonic Balance analysis, noise analysis, etc."
Screenshots at http://qucs.sourceforge.net/screenshots.html

Check the screenshots of KTechlab and QUCS