I'd like to get some inspiration, could be favorite developer docs, but also resources on how to make them great.

Examples:

Stripe (https://stripe.com/docs): probably the canonical example for dev docs, well written, well structured, sweet spot between code examples and explanatory text (e.g. https://stripe.com/docs/billing/quickstart).

Tailscale (https://tailscale.com/kb/): well written, well structured, lots of how-to guides.

Docusaurus showcase (https://docusaurus.io/showcase): aggregation of docs, some of them are great, some are not. All of them are open source so it's a useful resource for inspiration.

Also, not a doc itself but a great tool to build docs: https://codehike.org/