Heroku is a mature PaaS cloud-hosting solution that supports the development of Node applications. To get started, visit http://www.heroku.com and submit an e-mail address. Heroku is free to start with. After you've confirmed your account, you can start deploying apps right away.
Scaling Heroku applications involves increasing the number of dynos that you are paying for. Each dyno is an isolated container running your application and you are able to increase or decrease the number of dynos your application uses with ease. In this way, there aren't any hosting packages to buy—you simply scale as needed by asking for more, or fewer, dynos.
Heroku allows you to deploy applications on many platforms and languages—it is not Node-centric. This is something to keep in mind should you anticipate the need to add services to your application not written in Node.