Namecoin is a good example of this - decentralised domain registrations using the .bit TLD.

Namecoin is cool but I think there are still big issues to be fixed, like renewals/pricing to avoid one person getting all the good domain/sane names.

Yeah you're right - Namecoin has a massive squatting problem. It costs only pennies to register a name which doesn't help.

One possible solution is a proof of work for name registrations, similar to the Onion Name System [1]. There is a short talk by Jesse Victors that explains it nicely [2].

[1] https://github.com/Jesse-V/OnioNS-HS

[2] https://youtu.be/zZzOVKPcIMg

Aha! I was wondering when someone would say this!