Qucs (speak: kju:ks) is a circuit simulator with graphical user interface designed by Michael Margraf and distributed as a free software . Qucs abreviation from Quite Universal Circuit Simulator is able to perform many different kinds of simulation (e.g. DC, s parameter).
Qucs circuit simulator has a very nice interface and is not so complicate to use . You can use Qucs for drawing circuit diagrams for your projects or to simulate designed projects .
Multisim is a very useful and powerful SPICE software designed by National Instruments that can be used to design and simulate electronic and electrical circuits .
Multisim is a very complex easy to use simulation software that can be used for small ( low complex ) and huge complex electronic circuits .
Multisim SPICE software is not free but is very nice , the main menu is arranged in some way that helps you to design and simulate very quickly and easy any circuit .
TI Tina as is described on the Texas Instruments website is a free analog simulator . TI TINA SPICE-Based Analog Simulation Program is designed and distributed by Desig-Soft and Texas Instruments and is available for download in a free version, but you can update it to a paid version which include more features and libraries .
The interface of the TINA-TI SPICE-Based Analog Simulation Program is very nice and easy to use . You can draw a circuit in few minutes , without to require some special documenation about this software .