Tutorials
Tutorials help you get started with Nix. They'll take you through the basics of what Nix is and how to use it, allowing you to learn Nix with little or no prior knowledge.
Ryan Yin's NixOS & Flakes Book
Ryan Yin's nix book is a great beginner guide to using Nix with flakes. It takes you from first principles through flakes. This is a missing area in the Nix documentation, as flakes are still experimental. Despite their experimental status, flakes are used in a lot of real-world projects and can make some tasks much easier, so it is still a good idea to learn about them.
nix.dev - Tutorials
nix.dev is an official resource, owned and maintained by the NixOS documentation team. It has a section with tutorials which can get you up to speed on the language, packaging software, and NixOS modules.
Nix Pills
The Nix Pills are a series of blog posts by Luca Bruno. They largely cover the usage of the Nix language and package manager, without frills such as NixOS.
Guides
Guides help you get specific things done or teach you how to improve at using Nix. They'll assume some prior knowledge but may also need you to know specifically what you want to do.
nix.dev - Guides
nix.dev is an official resource, owned and maintained by the NixOS documentation team. It has a section with guides, including information about best practices.
Wikis
Other wikis, just like this one! Anyone can edit to share their knowledge.
Official NixOS Wiki
Despite the name, this wiki covers topics related to Nix, NixOS and Nixpkgs.
Lix Wiki
Manuals / References
Nix
Nixpkgs
NixOS
Search engines
Noogle
Searches Nix and Nixpkgs builtins and lib.
Searchix
Searches nixpkgs options and packages, as well as nix-darwin and home-manager options.
NixOS Search
Searches NixOS packages and options.
Home Manager Options Search
Searches home manager options.
Other
Nix Resources recommended by Lix
nix.dev
nix.dev is an official resource, owned and maintained by the NixOS documentation team.