Using parallel or loading external images or js

I have placed my $script variable in the footer.

I notice that sometimes the pages will load slowly because of external images or js. Gmap is a great example.

has anyone used parallel: http://drupal.org/project/parallel

to load external images, or js, css?

Would it be helpful to use it for internal js, css, and images too?

If you have experience with this, I would love to hear it.