Hello,
It depends on what you want to simulate.
On this page of the EDUCYPEDIA , you will find several links to them:
http://educypedia.karadimov.info/electronics/easoftsim.htm
There are more pages to electronics software over there:
Analog
Antenna design
Audio
Audio tone generators
Digital
Loudspeaker design
Measurement
PCB design
RF Antenna design
RF software
Stripboard Layout Software
Bertus
by Jake Hertz
by Aaron Carman
by Don Wilcher