The first major disappointment from my iPad was not being able to post pictures to my Drupal sites. The sites are using CCK, Filefield, and Imagefield. This is a great solution for any computer and OS except that iOS devices don't have a way to browse files so you can't upload them.
I just discovered Filefield Sources http://drupal.org/project/filefield_sources. It extends filefield, allowing a URL to be inserted so you can download images from the web directly to your site.