definitions.rb

define :apt_source do
  template "/etc/apt/sources.list.d/#{params[:name]}.list" do
    source "repo.erb"
    mode 0440
    owner "root"
    group "root"
    backup false
    variables(
      :url => params[:url],
      :distro => params[:distro],
      :component => params[:component]
    )
  end
  
  system('wget', '--quiet', params[:gpg_key_url], '-O -','|','apt-ket','add','-') if params[:gpg_key_url]
end

recipe

apt_source "percona" do
  url "http://repo.percona.com/apt"
  gpg_key_url "http://repo.percona.com/apt/RPM-GPG-KEY-percona"
  distro "lucid"
  component "main"
end

apt_source "percona" do
url "http://repo.percona.com/apt"
gpg_key_url "http://repo.percona.com/apt/RPM-GPG-KEY-percona"
distro "lucid"
component "main"
end

Forked; check out the comments there.