A simple Sinatra web app to upload a single file. Also available as a gist, based on http://pastie.caboo.se/134681

require 'rubygems'
require 'sinatra'

get '/upload' do
   erb '<form action="upload" method="post" enctype="multipart/form-data" accept-charset="utf-8">
   <input type="file" name="uploaded_data" id="uploaded_data">
   <p><input type="submit" value="Continue"></p>
   </form>'
end

post '/upload' do
   FileUtils.mkdir_p('./Uploads/')
   FileUtils.mv(params[:uploaded_data][:tempfile].path, "./Uploads/#{params[:uploaded_data][:filename]}")
   erb 'Upload Complete'
end