TheHittingVault.com is a great resource. Lots of drills and other resources. I used it when I coached high school softball. There are a ton of free videos and resources out there, but the problem is a lot of different drills and way of teaching things contradict each other. TheHittingVault isn’t free, but it’s comprehensive and consistent. It’s definitely not for everybody.
My son moves up to 10U this year, and I will be coaching my daughter’s 8U team. After 10 years of coaching high school varsity, I’m both very excited and a little apprehensive to work with these young gals!