Generation Genius is a website funded by the NSTA. The science materials cost $225/year. The website looks comprehensive in terms of resources and reminds me of PBS Kids. It offers videos, activities, readings, and assessments on different topics. I am too cheap to sign up for it now, but you can try it out for free for a month to see if it's a good fit for you.
I'm just a science teacher sitting at my computer generating and finding ideas to make learning more enjoyable.