Circuit design software?

So I bought my first Arduino kit and it's quickly become apparent that I should really know more about electronics if I'm ever going to come up with my own projects. So I'm reading through a book on electronics and thinking there must be software that helps map out circuits. I've googled a few, but thought I'd get the opinions of people here.

Is there a good (preferably free) circuit drawing and dare I say testing software (open source?) that people like?

I see there are some open source projects and a few free ones from circuit manufacturers, but I'm not sure which one I should put time into learning?

Thanks.

What is it your are trying to do? Is it draw schematic diagrams?

A friend likes qucs.
It's Open Source, and has a circuit simulator.

HTH
GB-)

I use ExpressPCB a schematic and PCB layout package - free, no simulation though. Eagle is very popular.

You may try this LTspice IV from Linear Technology

LTspice IV is a high performance Spice III simulator, schematic capture and waveform viewer with enhancements and models for easing the simulation of switching regulators. Our enhancements to Spice have made simulating switching regulators extremely fast compared to normal Spice simulators, allowing the user to view waveforms for most switching regulators in just a few minutes. Included in this download are Spice, Macro Models for 80% of Linear Technology's switching regulators, over 200 op amp models, as well as resistors, transistors and MOSFET models.

Is there a good (preferably free) circuit drawing

There's gEDA:

I'd like to add that although I started with Eagle, I wouldn't recommend it as a first program.

It's got a very steep (downright vertical to be honest) learning curve that's completely counterintuitive for beginners! After you know sort of what you're doing, I find it to be a great piece of software (but I still find myself using round-and-about methods of doing things that must have a simpler solution; try connecting a polygon to a trace...I dare you! ;D).

Good luck!

have a look at Fritzing: http://fritzing.org/

I know its not open source or free, but after trying MANY open source and free things for PCB and Schematic work... and getting frustrated over and over... I decided to spend a few bucks. (and only a few when you compare that with what most other vendors want you to pay)

Keeping in mind that I wanted simple to learn and easy easy to use, I don't regret buying ABACOM's SprintLayout and SPLAN.

http://www.abacom-online.de/uk/html/produkte.html

You CAN try these out before you buy.

TinyCAD.
http://tinycad.sourceforge.net/
open source, its not 'that hard' to learn.

TinyCAD netlists can be imported to FreePCB.

also open source

I have not yet found much similar that I like under Linux.

Where we can download the Arduino circuit design program. Can somebody help. The web site that shows this software is a bit confusing and it is not clear where to go to download this software.

www.cadsoft.de
for Eagle software. That's what the boards are designed in.
Example:
EAGLE files: arduino-uno-Rev3-reference-design.zip (NOTE: works with Eagle 6.0 and newer)
http://arduino.cc/en/uploads/Main/arduino_Uno_Rev3-02-TH.zip