Hello,
Can anyone recommend any decent software to simulate circuits. Something similar to multisim but affordable or free.
Thanks
I think that SPICE is the most mature and popular circuit simulation program around, used in most university programs and available free I believe from several sponsoring sites. Downloaded it once but found the whole simulation thing just too complex for my brain. I use oscilloscope, signal generators, and other test equipment in the 'old school' manner of circuit analysis. 
Thanks lefty. Looking at the SPICE homepage, it looks to be way more complex than what I'm looking for. MultiSim was really easy, drag and drop the components, drag wires from point to point, then click simulate. Trying to wrap my brain around the arduino is enough, SPICE looks like more than i want to tackle right now.
Linear offers "LTSpice".
I like to use the Java-based: Circuit Simulator Applet
And it's iOS Cousin: iCircuit
LTSpice is probably as good as you'll get without paying. Here's the link: Design Tools & Calculators | Design Center | Analog Devices
The advantage of using it over the "toy" simulators like Falstad: it's still real SPICE, you are learning a useful skill if you learn LTSpice. You can (with enough knowledge and practice) download SPICE models from part manufacturers and use them in your simulation.
It's almost entirely analog simulation, though characteristics of some digital elements are available. Typically you would use it to puzzle out a section of analog circuitry you need for interfacing with a sensor or whatever. Not try to simulate your entire project (unless your entire project is analog!).