InvisibLights
With Minecraft version 1.17, the game introduced its own invisible light sources, and this mod now utilizes them.
What is this mod?
Tired of having to fill your buildings with torches or glowstone blocks that ruin the aesthetics? InvisibLights solves this problem by providing the ability to place completely invisible light sources.
How does it work?
First, you'll need to craft a rod of light using the following recipe:

After crafting the rod, you'll need to have glowstone dust in your inventory. Now you're ready to light up your world! Placed light sources can be made visible and broken while holding the rod. Using glowstone dust on light sources allows you to adjust their brightness.
Demonstration
See how the mod works in action:
Visual comparison
Here's what a room looks like with traditional lighting:

And here's the same interior with invisible light sources:

Additional features
The mod adds only one item - the rod of light (there's also a technical block, but it doesn't require your attention).
To place a light source, hold the rod in your main or off-hand and right-click on a surface. Each placement consumes two units of glowstone dust (in survival mode).
To make all light sources visible, crouch and right-click with the rod. You'll hear a sound effect and see all placed sources, which can now be broken to retrieve glowstone dust. Repeat the action to hide them again.
Upgraded version
You can create an enhanced version of the rod by adding redstone:

The powered rod can be charged in any Forge Energy compatible charger and use stored energy to place light sources. Note that the powered rod version is only available for Forge.
Visualization
Hidden light sources:

Visible light sources:

Other video reviews
Additional mod demonstrations:
https://www.youtube.com/watch?v=iU8cxGIbbyE (by BioMasterZap)
https://www.youtube.com/watch?v=Y4t2MKk24as (by ClumsyMinecraft)