You should add Fritzing too. It's a very entry-level tool (as in focused on children and artists), and a bit buggy, but it definitely exists, supported quite heavily in the Arduino space, and is definitely free.
what about gEDA?
gEDA only works on Linux and MAC OS X.
So?? Some other packages work only on one platform. At least gEDA works on two platforms.
It's not that. gEDA is quite thoroughly stuck in the 80s. It may be great if you are the sort of person who doesn't flinch at that - some may even see it as an advantage... but really, it still follows the "UX" design principles of the days of CP/M and the first Unixes.
I once tried wrapping my head around it, and it just didn't feel worth it. Not with KiCAD around, now capable of doing controlled impedance tracks and other high-end stuff like that.