Use this page to grab a single-file OPML that contains RSS feeds of all your YouTube subscriptions. This feature used to be part of the YouTube subscription manager UI, but Google removed it for unknown reasons.
Click the link below to kick it off; Google will ask you to authenticate, and once you do, it will generate the OPML file for easy importing into readers like Feedbin, NetNewsWire, etc.
Don't worry, I don't keep your data or do anything with it. This is a JS-only page hosted on GitHub Pages, so I never see anything from you. If you find a bug or want to add a feature, the code is right here.