Vendoring rubygems without rails.rb

# mkdir vendor; cd vendor; mkdir gems; cd gems
# gem unpack rack
# gem unpack sinatra
# gem unpack haml
# gem unpack sequel
# gem unpack ruby-net-ldap
GEMS = {
  'rack'     => 'rack-1.1.0',
  'sinatra'  => 'sinatra-1.0',
  'haml'     => 'haml-2.2.23',
  'net/ldap' => 'ruby-net-ldap-0.0.4',
  'sequel'   => 'sequel-3.10.0'
}
# You can't just chdir to each, because one gem might require another (e.g. sinatra requires rack).
$:.unshift( *GEMS.values.map{ |path| File.expand_path( File.join('vendor','gems',path,'lib') ) } )
GEMS.each{ |gem,path| require gem }

Simpler, if less precise:
$:.unshift( Dir['vendor/gems//lib'] )