Rails 2.1.0 has, among other things, one very cool feature - named scoping.
class Whatever < ActiveRecord::Base
named_scope :active, :conditions => { :active => true }
end
Whatever.active #yields all active whatevers
Whatever.active.find(x) #only runs find() on active whatevers
You can even have parameters that get passed in through anonymous functions. It's a very powerful mechanism, and makes everything much more beautiful. Learn more here.