Installing from source has one pitfall, that removing (and otherwise keeping track of installed files) becomes difficult. It's best to let the package manager handle the installation. You can use this PPA and then apt-get will get you the latest version.

sudo add-apt-repository ppa:chris-lea/node.js 

sudo apt-get update

sudo apt-get install nodejs

The PPA has since been moved to another source. The instructions from the NodeJS Github wiki:

curl -sL https://deb.nodesource.com/setup | sudo bash -

sudo apt-get install -y nodejs

The commands, condensed out from the script:

sudo apt-get install apt-transport-https lsb-release curl 

curl -s https://deb.nodesource.com/gpgkey/nodesource.gpg.key | apt-key add -

sudo sh -c "echo 'deb https://deb.nodesource.com/node $(lsb_release -sc) main' > /etc/apt/sources.list.d/nodesource.list"

sudo sh -c "echo 'deb-src https://deb.nodesource.com/node $(lsb_release -sc) main' >> /etc/apt/sources.list.d/nodesource.list"

sudo apt-get update

sudo apt-get install nodejs