We have been using busy bags in our house from the time Mack was about 1. They are amazing for keeping kids busy in church, waiting rooms, airplanes, hotels, restaurants, etc. The general idea is that the activity is small enough to fit in a bag, doesn’t make a mess, and is quiet. I like to rotate them and keep a few different ones in my diaper bag at all times! I have heard of people doing busy bag swaps, where each participant makes busy bags for all of the children that will be at the swap, when you leave you will have a stash of busy bags for your child and you only had to make multiple sets of one bag. It sounds like a great idea to me!
This is one of my favorites, Ava (11 months) can play with them by banging them together and exploring the velcro while Mack (3 years) can build a variety of things with them.