I want to be able to create an RSS feed that I can share

I want to be able to create an RSS feed that I can share as a widget across the Multisite.

I known that Users can make their own RSS feeds but I was to make a few standardised Feeds (widgets) that people can easily utilise on their own sites.

I could use a third party site to make the RSS widgets, but am wondering how to acomplish this toally within WordPress.

Steve