Debian 6 comes with a outtdated version of node.js.
The node development is way faster than the debain version cycle, so if you want to use node for your application, you need to get one of the lastest version.
The easier solution to do that is to use NVM, it's a clone of RVM for Ruby. It allows you to install the version you want, and you can choose which version you going to use for every single project.
It's pretty easy to install, just do :
curl https://raw.github.com/creationix/nvm/master/install.sh | sh
Then you can install node, and use it :
nvm install 0.10
nvm use 0.10
All the docs are here : https://github.com/creationix/nvm