KiCad PCB EDA Suite

KiCad is a free and open source EDA (electronic design automation) software for editing circuit schematics, PCB layouts and component libraries, with Gerber and drill output.

Features
First released in 1992, KiCad is considered mature and is used for the successful development and maintenance of complex electronic boards. It doesn't impose limitations such as board size or number of pins, etc. and can handle multiple layers. Being open source it's an ideal tool for Open-source hardware projects. KiCad is available for Linux, Windows and Apple OS X (experimental, but working).

Libraries

 * KiCad libraries

Annoyances

 * One annoyance of KiCAD solved - F4 Drag, EEVblog forum, March 2012
 * All the ways KiCad annoys me, Head-Fi.org forums, Feb. 2015
 * I want to love KiCad, Reddit, Jan. 2016