HtmlEncoder is a web-application built on ASP.NET MVC 4, source-controlled on GitHub, deployed on AppHarbor.
GitHub allows you to directly deploy to AppHarbor on checkin/push to the Git-repository, which is a very powerful and useful feature, to quickly get your ASP.NET web-apps online in the cloud.
It started out with a need to encode strings for HTML and developed into a quick test of how Web API on MVC 4 works in an AJAX-enabled web-app.
Try it out at http://htmlencoder.apphb.com and fork it on GitHub.