Not bothering with things you can't host yourself. RSSMix is a popular free service that doesn't seem to be doing anything fishy, but it goes down a bunch.

• gbierman/RSSMerge
• simplepie/simplepie/
• huginn/huginn
• rawdog - HTML output by default, but can also generatea feed with a plugin.
• feed2toot posts from RSS to Mastodon, but it can do so from multiple feeds. You could take the Atom feed from the Masto account if you really needed to~~~~~
• chase-seibert/rsscombine

I assume to encourage you to make an account. In my experience tend to be shit websites I don't want to use! But they have people I want to keep track of :(

Arseholes.

• e-flux
• Facebook
• Soundcloud
• Twitter

• ✰ rss-bridge - Supports heaps of places, and people also contribute. Need to host, but there are plenty of websites setup that run it already. EG: bridge.suumitsu.eu
• TwitRSS.me - Very straightforward, enter someone's Twitter username and get an RSS feed. Also does Twitter searches.
• Queryfeed - Does Twitter, Facebook, Google+. Has a bunch more options. For examples get a feed of tags. Didn't like the Facebook page I fed it.
• ✰ getrssfeed - Soundcloud and iTunes. RSS-Bridge doesn't work for Soundcloud for me, but this fills the gap!
• IFTTT - Is a general tool for automating communication between programs. Somethings it helps here. Not a fan though.
• FetchRSS - General, needs registration.
• Feed Killer
• Selfoss - I think this in actually an RSS reader?
• Feeds API
• ✰ RSS Box - Nice and clear, supports lots of different places.
• Huginn - Like IFTTT, a general automation tool that can be used to generate RSS feeds.
• ✰ Kill the Newsletter! - Slightly different, turns E-mail newsletters into RSS feeds.

• For Facebook you have to run something to convert the JSON to RSS.
• Youtube actually uses RSS, it's just hidden. You can view the feed with the URL https://www.youtube.com/feeds/videos.xml?channel_id= and searching the page markup for the channel_id, or grab a browser plugin, etc.

Ones I need to follow-up on / research more.

• https://www.makeuseof.com/tag/12-best-yahoo-pipes-alternatives-look/

• Feeds are editable after creation (excludes non-signup ones I guess).
• Not dodgey.
• Maybe self-hosted, or even just a script I can build a page around.

• News Cycle - RSS-as-slideshow viewer you can build into your website.