The author has covered many good examples of freeware but obviously cannot list all of them. KiCAD is already fairly well known, as is LTspice. I think the author's intent is to list not-so-well-known freeware, and I applaud his efforts.
Readers' comments as to other good examples of freeware are very useful too, and add informative detail to the original article.
Page15 about Mach3: Unfortunately, the software is currently for Windows only, so Linux users will have to beg, borrow, or steal a machine outfitted with the OS until it's been converted.
You don't need to change the OS. For Linux there is LinuxCNC (originally known as EMC2, enhanced machine controller). It's based on a realtime extenstion to the Linux kernel (Xenomai) for the critical parts and a GUI. It also includes a ladder-logic PLC to automate parts of a machine. The G-Code preview is rendered using OpenGL.
There is a quite strong community around LinuxCNC (as with Mach3 as well), both are used very successfully to retrofit old machines (with broken controllers or to upgrade manual machines).
EasyEDA is a free web-based EDA tool. It's still under heavy development and has a few rough edges but is pretty powerful stuff. It's quite unusual too because although it offers a very low cost PCB service, there's no tie-in them: users can download Gerbers and have their PCBs made by any supplier.
I am a fun of free DIY tools and I am aware of several tools that are helpful and can be found for free. Nowadays there are many useless tools available on net and will not help you at all. They may be useless in the sense that they cannot posses the feature you are looking forward to use at that time. Some tools are worthy and are very effective. I think when designing a DIY tool, before you post it on net for free, you should make sure that it is perfect and can help in as many ways as possible.
I was looking Calculatoredge. This is indeed a good tool for high school and engineering students. But it will be more helpful if these tools can be ported in SmartPhone (like an andriod app). Also besides calculation if it can explain the logic behind the calculation then it will be great.
May be the above two will be applicable for the other tools also
Thanks a lot for bringing the collection of very nice and cool Free list of simulators many of them were not know to me, but now I will try many of them and will promote them as well.
I would like to recommend the users the site http://www.osalt.com/, at any time if you are in need of a paid software but do not want to spend you can look for the open source alternative on this site.