I recently did a fresh install of Ubuntu 12.10 on a new hard drive I bought. One of the first things I do when installing a new system is setting up my development environment, which I'm very happy to say now includes Node.js. I've had a few problems getting Node.js, MongoDB, and some dependencies set up previously, but this time I used the <s>Rock Solid Node.js Platform on Ubuntu</s> script, which worked perfectly!
It has a couple of simple options you can set, whether you want to use
aptitude, and you can choose to include MongoDB and/or Redis. Then just copy the code from the "get link for my script" button into the terminal, and about a minute later you're up and running.
UPDATE: Unfortunately, the original site was taken down.