What's the easiest method to run Ruby scripts using Apache with no framework (much like PHP scripts)?

Bonuses when the script can access the HTTP request stuff (URL, host, GET/Publish params and cookie). If your framework is completely needed, the most lightweight which may use Apache?

Use Apache with mod_rack and also the Rack interface to speak using the server.

Try Sinatra and you will write something similar to this:

require 'sinatra'
get '/hi' do
  "Hello World!"

It's really a framework, however the littlest application on Sinatra is a lot more compact than littlest application on Rails.