http://www.linear.com/designtools/software/ltspice.jsp
http://www.labcenter.co.uk
http://www.softsea.com/review/Electronic-Design-Studio.html
http://qucs.sourceforge.net
http://free-vk.t-com.hr/aljuba10/croatian/programi.html
http://www.ni.com/multisim/try/
http://en.wikipedia.org/wiki/NI_Multisim