Food lab is a great series of videos from the University of Queensland and an Australian Masterchef finalist discussing and demonstrating the science of food.
ABC Splash has free resources and games on a variety of topics, searchable by keyword, curriculum area and Australian school year.
NASA for students has a variety of free NASA content on everything to do with space and related science and technology with filters for different age groups. It's complemented by the NASA YouTube channel.
PBS Learning Media has a mixture of free and paid learning resources on a huge variety of topics, sortable by school year, by subject area and by the type of resource.
Kids Discover Online is a searchable and browsable online repository of kid-friendly resources on a huge variety of educational topics. There is some free content here, but for around $60 per year - depending where you are - you can get access to over 1000 resources. The huge bonus with these is that they're very... Continue Reading →
Love Nature is a streaming video service with a mind boggling array of full-length nature and life-science documentaries. There is no free content here, but a subscription is less that $5 per month - depending on where you are - and the content may be viewed on most devices.
TED Ed has free videos and animations on a variety of educational topics and is sortable by learning level and topic.
Ask an astronomer is run by volunteers in the Astronomy department at Cornell University. It's a free resource that includes an abundance of weird and wonderful details, facts, stories and images on all things astronomical.