Index: app/controllers/users_controller.rb
===================================================================
--- app/controllers/users_controller.rb	(revision 3840)
+++ app/controllers/users_controller.rb	(working copy)
@@ -69,6 +69,11 @@
     end
     render :layout => 'base'
 
+    respond_to do |format|
+      format.html
+      format.xml
+    end
+
   rescue ActiveRecord::RecordNotFound
     render_404
   end
Index: app/views/users/index.xml.builder
===================================================================
--- app/views/users/index.xml.builder	(revision 0)
+++ app/views/users/index.xml.builder	(revision 0)
@@ -0,0 +1,12 @@
+xml.instruct!
+xml.users :type => 'array' do
+  @users.each do |user|
+    xml.user do
+      xml.id     user.id
+      xml.first  user.firstname
+      xml.last   user.lastname
+      xml.login  user.login
+      xml.mail   user.mail
+    end
+  end
+end
Index: config/routes.rb
===================================================================
--- config/routes.rb	(revision 3840)
+++ config/routes.rb	(working copy)
@@ -171,6 +171,7 @@
   map.with_options :controller => 'users' do |users|
     users.with_options :conditions => {:method => :get} do |user_views|
       user_views.connect 'users', :action => 'index'
+      user_views.connect 'users.:format', :action => 'index'
       user_views.connect 'users/:id', :action => 'show', :id => /\d+/
       user_views.connect 'users/new', :action => 'add'
       user_views.connect 'users/:id/edit/:tab', :action => 'edit', :tab => nil