adding observers outside environment.rb

I need to add an ActiveRecord observer and thought I should follow
Rails 2 intent by not changing the base environment.rb
I create a file config/initializers/observers.rb but don't know what
to add to it.

I can't add: config.active_record.observers = :user_observer
Since "config" isn't defined in the scope of the initializer file and
I don't know if it would be harmful to add a "Rails::Initializer.run
do |config| " block.

So, is there a method to add an observer outside the environment.rb
initializer block?
Or is it ok to have a second initializers block in my other
"initializers/" files?

thanks, Jon