Useful links
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Main website:
http://kicad-pcb.org

Users mailing list:
http://tech.groups.yahoo.com/group/kicad-users/

Developers mailing list:
http://launchpad.net/~kicad-developers

Code repository (contributions are welcome):
https://code.launchpad.net/kicad

Official footprint repositories (contributions are welcome):
http://github.com/KiCAD (all repositories with '.pretty' suffix)

Official schematic parts and 3D models library repository:
https://github.com/KiCad/kicad-library

Library developers mailing list:
https://launchpad.net/~kicad-lib-committers

Official documentation repository:
https://github.com/KiCad/kicad-doc

Documentation team mailing list:
https://launchpad.net/~kicad-doc-devs

Daily builds of product branch PPA (for Ubuntu):
https://code.launchpad.net/~js-reynaud/+archive/ubuntu/ppa-kicad

Git mirror
https://github.com/KiCad/kicad-source-mirror
(Patches should be submitted to the dev mailing list, because as a mirror, pull requests are not supported.)

Useful Tools
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A separately maintained project that assists in building from source on
Windows:
https://launchpad.net/kicad-winbuilder

A script which automates the download and installation of footprint libraries
from github.com, should you decide not to use the standard "Github" plugin
for this same purpose:
http://bazaar.launchpad.net/~kicad-product-committers/kicad/product/view/head:/scripts/library-repos-install.sh

Original Author's site:
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http://iut-tice.ujf-grenoble.fr/kicad/