Can you recomend a freeware simple Electronic board CAD software?

I have just started with bread board electronic circuit, which is nails on a wood board connected by wires and Components. I have made a flasher which is just 2 flashing LE-D's, But is there a free program to Design and test a virtual circuit board? were you physicaly place components andConnectt them to see the results? I do have a physics program at school that does it sort what im talking bout its called crocodilee physicss" is there a free circuit board designin softwar spicilyly made for electronics, were you make and test you creationsn virtually lbeforeo actually making them in real life?