Assuming you are using factory girl!!

In your db/seeds.rb file add

require 'factory_girl'
Dir[Rails.root.join("spec/factories/*.rb")].each {|f| require f}

10.times do
  Factory.create :user
end

This assumes a factory file spec/factories/*.rb

Factory.sequence :email do |n|
  "somebody#{n}@example.com"
end

Factory.define :user do |f|
  f.email { Factory.next :email }
  f.password 'testing'
  f.password_confirmation 'testing'
end

then

rake db:seed 

will fill you db with goodness straight from the factory.