Our deploy for unicorn. It also has magical powers.

unicorn_capistrano.rb

set :unicorn_pid, "#{current_path}/tmp/pids/unicorn.pid"

namespace :unicorn do
  desc "start unicorn"
  task :start, :roles => :app, :except => { :no_release => true } do 
    run "cd #{current_path} && #{try_sudo} bundle exec unicorn_rails -c #{current_path}/config/unicorn-#{rails_env}.rb -E #{rails_env} -D"
  end
  desc "stop unicorn"
  task :stop, :roles => :app, :except => { :no_release => true } do 
    run "#{try_sudo} kill `cat #{unicorn_pid}`"
  end
  desc "graceful stop unicorn"
  task :graceful_stop, :roles => :app, :except => { :no_release => true } do
    run "#{try_sudo} kill -s QUIT `cat #{unicorn_pid}`"
  end
  desc "reload unicorn"
  task :reload, :roles => :app, :except => { :no_release => true } do
    run "#{try_sudo} kill -s USR2 `cat #{unicorn_pid}`"
  end

  after "deploy:restart", "unicorn:reload"
end