include Rails.application.routes.url_helpers

# set host in default_url_options:
default_url_options[:host] = "localhost"

# can then use:
url_for()

# can check existing routes:
edit_user_url(User.first)
=> "http://localhost/user/1/edit"

in Rails 2, use `include ActionController::UrlWriter` instead.

To access url helpers (url_for, etc) from Rails console (Rails 3)

rails

Rails