I like these link aggregators by Peter Krumins. Also:

https://mathurls.com/
https://hwurls.com/
https://techurls.com/
https://tuxurls.com/

This is a large collection of single purpose, chainable (like a pipeline) tools for text and image processing (csv conversion, etc) and other tools that are written in javascript and run in the browser. I'm impressed whenever I come across one of them (and they've been useful to me a few times).