AutoDesk 123D Circuits
NOTE: The 123D line of programs from Autodesk has been moved. The (former) 123D Circuits program is now available through Autodesk's Tinkercad collection of programs. The3 link below has been updated.
123D Circuits is an electronics simulation program for designing circuits. It is an online program that allows you lay out components on a breadboard and simulate how the circuit will behave, it can also create schematics and model the circuit on a printed circuit board (PCB), and can even order manufactured PCBs direct from the company.
123D Circuits is free software provided through the AutoDesk 123D collection, anyone can use it for free. Sign-up is required.
Install Link: https://www.tinkercad.com/
There are a number of tutorials and videos provided at https://123dcircuits.zendesk.com/hc/en-us/articles/202254759-How-To-s-on-Instructables-com as well as other online resources.