Embed videos, images, PDF, and article previews from "any" source with just the URL. Just add your Embedly Key to the Embedly plugin setting
You can sign up for a free or paid plan by clicking here.
In the post editor click the Embedly icon and add your URL.
You need a key to embed "any" url, otherwise the plugin will only be available for these providers.
If you upgrade to the Embed paid product (http://embed.ly/embed) it will remove the powered by Embedly logo, and allow higher levels of usage and support.
Yes, see steps above to install for multi-site. Note: You will need to activate Embedly for each site.