Ran into an issue today where I couldn't get npm to install to find the correct packages after doing a normal node/npm install. I just kept getting the error:
Error: Cannot find module <module>
Quickly, found that you need to use a different repository before installing:
apt-get install python-software-properties apt-add-repository ppa:chris-lea/node.js apt-get update
Once you do that you should have node and npm installed correctly and should be good to go.