A simple application written in Ruby, using the Sinatra framework. Hopefully it should be easy to read even to those who don't know Ruby.
To run it, just do:
rackup
And the application should be accessible at http://localhost:9292.
If you want to know more, have a look at our blog post covering HTML5 file uploads
This example includes and uses a piece of middleware called Rack::RawUpload, also by us. It makes handling this kind of uploads much easier.