Dion Hulse

This plugin offers limited support. Please do not expect new features or too many bugfixes. Features may be removed at any time.
Add From Server is designed to help ease the pain of bad web hosts, allowing you to upload files via FTP or SSH and later import them into WordPress.
This plugin is NOT designed to.. 
 * Be used as a replacement for the file uploader 
 * Be used for migration of websites 
 * Re-import your files after moving webhosting 
 * Batch import media
This plugins IS designed to.. 
 * Import files which are larger than your hosting allows to be uploaded. 
 * Import files which are too large for your internet connections upload speed.
WordPress does a better job of file uploads than this plugin, so please consider your needs before you use it.
You may also want to look at using WP-CLI for media import purposes: 
https://developer.wordpress.org/cli/commands/media/import/

Add From Server

Whenever I need to upload media files that are too big to upload directly to WordPress, I FTP them to the server and use this plugin to add them.

Great tool for those big media files you can only ftp to the server

Add From Server is designed to help ease the pain of bad web hosts, allowing you to upload files via FTP or SSH and later import them into WordPress.

joetan

This WordPress plugin allows you to use Amazon’s Simple Storage Service to host your media for your WordPress powered blog.
Amazon S3 is a cheap and cost effective way to scale your site to easily handle large spikes in traffic (such as from Digg) without having to go through the expense of setting up the infrastructure for a content delivery network.
Once setup, this plugin transparently integrates with your WordPress blog. File uploads are automatically saved into your Amazon S3 bucket without any extra steps. Once saved, these files will be delivered by Amazon S3, instead of your web host. Any image thumbnails that get created are saved to Amazon S3 too. You’ll also find an “Amazon S3” tab next to your regular “Upload” tab, which allows you to easily browse and manage files that were not upload via WordPress.
<h3>Documentation</h3>
If you need more help installing and configuring the plugin, <a href="http://code.google.com/p/wordpress-s3/wiki/Documentation" rel="nofollow ugc">see here for more information</a>.

Amazon S3 for WordPress

Allows you to mirror your WordPress media uploads over to Amazon S3 for storage and delivery.

Add From Server vs Amazon S3 for WordPress