calum.me – Calum Benson's Bits & Pixels

Note: This extension is not associated with RSS Menu from e dot studios, or any similarly-named application.

What Does It Do?

Adds a menu button to your Safari toolbar that lists available RSS, Atom and RDF feeds
Can open discovered feeds in most Mac newsreader apps (Vienna, NetNewsWire etc.), or preview directly in Safari
Toolbar button badge shows number of discovered feeds on current page

Visual refinements and essential bug fixes.
Updates to the jfeed library
Removal of the YouTube feeds code, which hasn’t worked for some time because Google no longer provides an API.

This extension will not work in macOS Catalina (or Mojave if you have updated to Safari 13). Starting with Safari 13, Apple has discontinued support for standalone extensions, in favour of App Store apps that bundle extensions.
Resizing the Safari window can occasionally cause the extension toolbar menu items to stop working. If this happens to you, go to Safari Preferences and disable the extension, then re-enable it.
In Safari 8, 9 and 10, when you try to open a feed in your RSS application, you will see an alert message asking if you want to add the feed to your Shared Links:

Click Cancel to continue opening the feed in your RSS application.

This issue does not affect Safari 11, as Apple has removed the Shared Links feature.
RSS Menu cannot open feeds directly in RSSOwl. This is because RSSOwl does not register itself as a feed URI handler on OS X as it ought to.
Extra YouTube functionality is no longer available. The Favourites and Recent Subscriptions feeds are no longer available when visiting YouTube user profile pages. Google have deprecated the v2 API the provided these feeds, and there is no equivalent in v3.

RSS Menu extension issues are tracked on GitHub, where you can also find the source code.