Is there something you find genuinely cool and would recommend ? Some webpage, program, OS, library or anything ?

I mean hey. There are SO MANY reaaaally cool things I didn't know until last few months.. Things I'd be so grateful for if I knew them earlier. I'll list some of them and I just know you have few of yours too. Feel free to educate the rest!

Processing - Program so fun to code in + CodingTrain(YTB channel)
Microcorruption.com - so freaking awesome if you wanna learn hacking / assembly (not x86 necessarily)
LiveOverflow - cool hacking channel
Radare - cool cmd Linux disassembler
vim-adventures.com - LEARN VIM (not just how to quit it) LITERALLY by playing a game!!!!!!!!!!!!!!
slashdot - stay updated , like really
"BEST-WEBSITES-A-PROGRAMMER-SHOULD-VISIT" - GUYS THIS! Sorry for caps but search this on GitHub and you will fucking die of happiness of how freaking useful links there are and no bullshit to dig through , just pure awesomeness. REALLY
HandBrake - Top media converter without bullshit and bloat stuff in it
Calibre - Best eBook management software capable of literally everything ebooks related. Kindle is a bloated joke compared to this
QubesOS - You know you can have every OS running at once - you have a Linux but are playing win games. Yup. It's there. Free
Computerphile - You all know it, it's just for completeness
Khan Academy - Same
VulnHub - download vulnerable VMs and hack them, or learn by reading writeup on how to do it!
Valgrind - MUST HAVE for C/C++ programmers
Computer Science crash course videos

That's all I can think of from top of my head but hey, there's more to it so definitely add your 2 cents!

Last thing, if nothing, just check the websites on GitHub, that's lifechanger

Looking forward to see some cool links & recommendations!