getting one column or method from AR find

for a current project i'm working on, there are certain actions which
trigger emails to be sent out to users.

currently i'm using something like users = User.find(:all, :conditions
=> '....')

and then looping through all of the users in the collection and adding
their email address to an array.

i'm sure there has got to be an easier way to extract just that column
of information to either a hash or any array right?