I’ll start with one of the most useful singular list of lists on the internet.
https://github.com/topics/awesome
“An awesome list is a list of awesome things curated by the community. There are awesome lists about everything from CLI applications to fantasy books. The main repository serves as a curated list of awesome lists.”
Just about anything you can think of is within this list. Enjoy!
PS: Thank you mods for your work moderating submissions. The quality and relevance of posts here is refreshing. This has to be my favorite community on Lemmy.
CyberChef - a web app for encryption, encoding, compression and data analysis
Diagrams.net AKA draw.io - a web/desktop app for creating diagrams, flow charts, tables, infographics, or maps of networks or relationships
What Unicode character is this? - Input a string, and get back the Unicode code point and character name for every character in the string