ACNH Apps

Animal Crossing New Horizons Apps is a website with useful apps for you to use.

A quick overview:

DIY Profits lets you note all the materials you want to "get rid of" and shows what the most profitable item to craft is.

Craftulator lets you note all the diys you want to craft or order from someone and shows what and how many materials you'll need for all the items.

Encyclopedia is a representation of the in-game encyclopedia
Use this to look up critters that you haven't caught yet, to see when and where they're available.

Calendar is an interactive calendar.
Click on the arrows to go to the next or previous months. Click on any day to see the specifics of that day. Click on the month to jump back to the current date.

More Websites speaks for itself. Other websites I've come across that are useful with playing the game.