There's a list of hidden RSS feeds from 2012. I believe that some of these feeds also offer alternative sorts.
The reason I ask is because I'm thinking about subscribing to new question feeds using a service that converts an RSS feed to email for entire sites. There are some services that will access an RSS feed on a regular basis and convert new posts to emails. Ideally, I wouldn't have to use this service, but there hasn't been much work done to help improve the discoverability of questions that I, as an expert in certain topics, can answer across the network. However, I'm concerned that because these are "hidden" and the links to them are non-obvious in the UI, that they may be deprecated without warning, putting me right back to where I am.
I'd also like to throw out the idea that if the RSS feeds aren't in danger of going away that they are made more obvious on the views that they relate to. For example, in the Questions view, I'd expect to see a reference or link to the RSS feed that exists for that view (including any applied sorting). I believe that this would give me more confidence in the fact that they won't be going away.