How to use Heroku to host static files

Here's a sample app that utilizes Rack's Directory module to serve up a directory listings of your app. Basically, all you need to know is that:

run Rack::Directory.new('.')

...will serve up the contents of your app as a directory listing. The sample here adds a few more embelishments such as a modified template and support for etags for browser caching.

You can see a sample of this app here.