If you want to host you webapp somewhere and test/present it for free, you can use the free service given by Heroku or Openshift by Red Hat.
Heroku – www.heroku.com – is a good place to get a free web host. It supports most of the web programming languages like Ruby, Node.js, Clojure, Java, Python, and Scala. If you need database you get a 5 MB database for free.
You just need to push your app to your server via git to deploy it.
You can get started with heroku here – http://devcenter.heroku.com/articles/quickstart.
You would also learn how to use git (a version control software) to be able to deploy your application on heroku. For the first timers, it would take some time to get your application running on heroku. Once you are done, you will have a http://<some_arbitrary_name_if_you_have_not_specified>.herokuapp.com kind of url to access your application.
OpenShift – www.openshift.redhat.com is a similar (free) service . Choose the express option at https://openshift.redhat.com/app/platform to get started. It follows similar strategy as that of heroku.