simulation of 555 astable mode

Does anyone know of a program (free!!-downloadable) which I can use to simulate 555 timer in astable mode- I also want to use it to simulate frequency modulation via an input to the control pin 5- I want to see the square waves produced.

ive tried Orcad 9.1 Pspice and I couldn't get it to work

Thanks

SwitcherCAD from Linear Technology is a totally free, uncastrated simulator. It comes with a model of the 555, and I believe it has 555 simulation examples to get you started.

try multisim, its free, it already has 555 configurations ready to be dragged and dropped and to be connected to any circuit, it also has oscilloscope, wattmeter, volt/ohm/ammeter, and many more test instruments; and it contains almost all electronic components. It's very user-friendly(drag and drop style). The oscilloscope is very nice, you can choose time per division etc. Just google it. I remember that it is a bit large, about 163MB, but it's worth the trouble. if you don't have broadband connection for fast downloading, find a friend who does! because this software is really great!