Hi,
I wrote Apache::RailsDispatcher to run Rails applications on mod_ruby.
  http://blog.shugo.net/articles/2005/08/03/running-rails-on-mod_ruby
Apache::RailsDispatcher can run multiple applications in the same
process. It works like this:
    * require loads libraries into the top level, and they are shared
with all applications.
    * require_dependency loads libraries into an anonymous module for
each application.
    * In the development environment, the anonymous module is orphaned
on each request. So required_dependency loads libraries every time.
    * In the production environment, the same anonymous module is used
for the same application. So required_dependency loads libraries only at
once.
    * Rails configurations such as ActiveRecord::Base.colorize_logging
are reset on each request.
This hack is just a workaround until YARV supports multiple VM
instances. We can get it in the near future, I hope.
Shugo