[joshschreuder]

See also:

- Wechall

- OverTheWire

- SmashTheStack.org

- CryptoPals.com

- Google Gruyere appspot

[travmatt]

I've been working through https://guyinatuxedo.github.io/ while reading "The Shellcoder's Handbook" and Sam Bowne's class notes (https://samsclass.info/127/127_F19.shtml). Highly recommended

[cjbprime]

And:

- https://pwnable.tw

- https://pwnable.xyz

[saagarjha]

https://microcorruption.com/ is also quite fun!

[strictfp]

http://www.try2hack.nl/

[thde]

And

https://www.hacking-lab.com/

[hakmad]

And: https://github.com/zardus/wargame-nexus

[larsnystrom]

In my youth I learnt a thing or two from hackthissite.org.