I came across this great resource for RSS today: Open RSS
Put in a URL, and they’ll grab a feed for it. They were able to do this for The Globe and Mail, which AFAIK has never allowed you to subscribe by RSS.
They also have instructions on how to get feeds for popular sites such as Reddit and Facebook. Plus there are guides on various aspects of RSS, and a huge filterable list of apps.
The About page alone is quite detailed, even showing their finances.