Installing Node.js via package manager

Debian

Node.js is available in official repo for Debian Wheezy(testing) and Debian Sid(unstable).
For Debian Squeeze:

root@host: ~ # echo deb http://ftp.us.debian.org/debian/ sid main > /etc/apt/sources.list.d/sid.list
root@host: ~ # apt-get update
root@host: ~ # apt-get install nodejs # Documentation is great.

Ubuntu

Example install:

sudo apt-get install python-software-properties
sudo add-apt-repository ppa:chris-lea/node.js
sudo apt-get update
sudo apt-get install nodejs

It installs current stable nodejs on the current stable ubuntu.

On openSUSE BuildService

Node.js stable repos list.

Available RPM packages for: CentOS 5; Fedora 13; openSUSE 11.3 and Factory.

Example install on openSUSE 11.3:

sudo zypper ar http://download.opensuse.org/repositories/home:/SannisDev/openSUSE_11.3/ SannisDevBuildService 
sudo zypper in nodejs nodejs-devel

Arch Linux

Node.js is available in the Community Repository and npm is available in the AUR.

Using an AUR tool(packer or yaourt) to install:

yaourt -S nodejs
yaourt -S nodejs-npm

Or grab the PKGBUILD and build it yourself using makepkg

OSX

Using a package

Simply download and double-click.

Using homebrew:

brew install node

Using macports:

port install nodejs  

Windows

Note: Windows builds are not yet satisfactorily stable but it is possible to get something running.

Using chocolatey:

cinst nodejs