Simulation software

What's a good piece of software for circuit simulation? It doesn't need to be too big in scope, just simple, hobbyist stuff. I remember using something in high school that just had a collection of basic parts and ICs and so on and let you design a circuit and "run" it to see what happened. Paid or free, doesn't matter, just so long as it's simple to use.

I use this one: http://www.falstad.com/circuit/

And it's iOS cousin, iCircuit.

LTspice is a good choice. It is a spice simulator that is free to download. It is well supported, so it should be easy to get going. A good location is: http://tech.groups.yahoo.com/group/LTspice/

Hi geotek I tried to install LTspice, but got this message "this is not a valid 32 bit program"

I'm using Windows Vista Home Basic. I tried to run the setup as win xp compatible, but same result. Which OS are you using?

Thanks

I'm running it on Windows 7 in 64 bit. I'll try it on a 32 bit machine. I've been using it for years on several machines, so I'm suprised you're having this problem.