Best (free) circuit design / sim software?

Just got my first arduino and I'm going to ask a few questions here in the future, I'm sure. Browsing through, I see some decent images of circuit designs, and I'm wondering what people are using or would suggest.

I'm hoping to find something free (this is a hobby, not work) that: * Generates or allows you to create decent looking schematics for review by other people * Does simulation. Not perfect, but PWM signals, transistors, handle saturation and switching speeds, etc

Bonus if it can do PCB design and optimization :). Double bonus if it works both in Linux and Windows (I can easily switch to either OS if a good program warrants it).

So how about it? What are you folks using?

ltspice, bar none.

hi-

"I" personally do not know or have used an all-in-one program with everything you asked about..

but for most schematic and pcb/layout design stuff.. I taught myself a bit about Eagle.. which seems to be a widely used program by many.. with many tutorials/support..etc.. (was a bit 'odd' at first.. but now I really enjoy it)

Others have used KiCad, DipTrace..and a few others..

for SIM software.. not to sure to be honest..(like to find some nice, and easy one myself if intuitive enough to use)

I remember this older one:

http://www.falstad.com/circuit/

Also for graphical diagrams and I think other features (pcb design/schematics too?)...

I like to use Fritzing (http://fritzing.org/) to post diagram of how things are physically wired up with my Arduino/components..

Thanks to both of you. I'll give them a shot and see what works best for me!

TI offers a customized version of TINA on its website. Quite capable of a spice simulator.