Auto Save Remote Image

The purpose of this plugin is very simple - when a post is published, it will fetch the first remote/external image that is referenced. The image that is retrieved is then attached to the post as the featured image. There are no settings to configure. Please do not use this plugin to violate copyrights. Sample uses: You maintain multiple blogs; copy paste the post contents from one blog to the other and this plugin will automatically save the first external image to the second blog. There is no need to re-upload images to multiple sites. This plugin can also retrieve and save images from sites like Flickr, Facebook, Picasa, etc.

Extract the zip file and just drop the contents in the wp-content/plugins/ directory of your WordPress installation and then activate the Plugin from Plugins page.