snippet.rb

# cookbook/ftp_stuff/definitions/ftp_user.rb
define :ftp_user, :password => nil do
  begin
    r = resources(:template => "/etc/ftp_passwd")
  rescue
    r = template "/etc/ftp_passwd" do
      owner "root"
      group "root"
      mode "0600"
      cookbook "ftppasswd.erb"
      variables({}) 
    end
  end
  r.variables[:users][params[:name]] = params[:password]
end

# cookbooks/bobo/recipes/default.rb

ftp_user "bobo" do
  password "monkey"
end

ftp_user "tclown" do
  password "clones"
end

# cookbooks/ftp_user/templates/default/ftppasswd.erb
# Will print every ftp_user
<%- @users.each do |u, p| %>
<%= u %>:%<= p %>
<%- end %>