Here is a collection of resources for HTML5 game development. There is a generic mega-list with more resources (not just related to HTML5) at Pixel Prospector.
- Download the latest version of Phaser.
- Phaser's documentation.
- Phaser's examples: official collection of Phaser examples. This is an excellent place if you want to do something but have no clue about which parts of Phaser API's you should use.
- HTML5 Game Devs forum: a great place to ask questions or showcase your game.
- How to succeed at making one game a month: an article that describes a great approach for indie or solo development. A must-read if you are a beginner at making games or struggle to finish your projects.
- Itch.io: a game publishing portal for indies, with lots of free games as well. It's great to see what others are doing, and perfect for inspiration.
- Finishing a game: an article about focusing on finishing projects and not getting derailed, by the creator of Spelunky.
- Surviving Ludum Dare: recommendations to succeed at Ludum Dare or other game jams.
- Kenney's art assets: multiple art packs, with professional quality, released in the public domain.
- Open Game Art: a collection of different art assets –sprites sound effect, music tracks, textures…– released under a license that allows re-using (sometimes under certain constraints).
- freesound: Sound and music, released under a Creative Commons license.
- Phaser: 2D game framework.
- A-Frame: framework for virtual reality experiences and games.
- PlayCanvas Engine: 3D game engine.
Here are some of the game development engines that support exporting to HTML5.
- Unity: 3D engine with support for many platforms and a very large community.
- Unreal: 3D engine used from indie games to blockbuster AAA titles.
- Game Maker: 2D game engine, beginner-friendly, and very popular among indie developers.
- PICO-8: a fantasy console that allows you to create small games with LUA and export them to the Web.
For a more exhaustive list, check out the Engine & Tools page at the MDN.