What CAD software are you using and why?
I use Solid Egde 2D Drafting - free version
It's "free" (you need to register). I tried many of CAD programs, both free and full versions (including Autocad, Microstation, QCad, VariCAD.....) and this was only one intuitive enough for me to start drawing immediately without any tutorial.
I use SketchUp, mainly for importing 2D files from Solid Edge. Again this was only software simple enough for me to start with. I tried full version of SolidEdge, after one tutorial for making 3D component I gave up to ever learn this on my own. Those proffesional 3D CADs have way of work something called history based modelling....? Maybe someone would explain this
For many years I work with Eagle. This is choice of many, APM is done in this one.
Why? It is simple, supported, well workin, multiplatform and also has free version.
In my previous job I designed PCB in relatively unknow software Formica. It has some features much more usefull and more clever than Eagle, but has major drawbacks for our use.
Other support software for design work
Irfan viewer - basic image resize, crop, change file type.
Inkscape - once used for drawing curves over scanned image
Gimp - used once for joining scanned pictures
Notepad++ - Must have text editor
Windows Paint - expensive, but really great bitmap editor :-D
Windows Snipping Tool - expensive, dead simple and useful
Siemens NX 7.5 - Has all the features (and more) that I could ever want.
AutoCAD Inventor - Easy to use
AutoCAD 2011 - Been using it for many years and at this point it's easier than trying to go to something else.
Eagle - Easy to use and almost everything has an eagle file for reference.