To help in data pack development, I currently use several online resources.

Online data pack repositories and code

misode has online generators, but I personally like to dive through the code they have available on GitHub.

Other useful data packs are:

• Dreamland
• Wabi Sabi Structures

Online content creators

I follow a few content creators that have a more technical view on data packs (and mods), or frequently give a list of recent/new data packs. The list below is in alphabetical order:

• AsianHalfSquat regularly reviews mods.
• unsorted guy has plenty of videos in which he plays custom modded minecraft worlds, together with his friends. His videos are inspirational to show what one can do within Minecraft with data packs and mods.
• WafflesAreBetter has videos on the more technical minecraft side, such as structure blocks, data pack development, custom dimensions, etc.