nQuake
A QuakeWorld package containing everything needed to play QW right now
NOTE: THIS PROJECT HAS MOVED TO GITHUB.
Download from http://nquake.com
Source code: http://github.com/nquake
QuakeWorld is a very fragmented game. Installing QuakeWorld involves installing Quake, downloading a client, downloading textures, scripts, addons, maps and much more. nQuake does all this for you with a simple online installer. nQuake always installs a completely updated package of QuakeWorld that simply works.
nQuake has become the standard within QuakeWorld, so even if you don't like the content of nQuake, it's a very good base for your installation. If you run into problems - simply install nQuake fresh and modify it until you are satisfied. Getting help with issues you bump into will be a lot easier if you started out with nQuake.