A non-exhaustive list that might help those affected by school closures due to coronavirus, compiled by the home educators community.
Khan Academy
Especially good for maths and computing for all ages but other subjects at Secondary level. Note this uses the U.S. grade system but it's mostly common material.
Epic!
Instantly access 35,000 of the best books, learning videos, quizzes & more
BBC Learning
http://www.bbc.co.uk/learning/coursesearch/
This site is old and no longer updated and yet there's so much still available, from language learning to BBC Bitesize for revision. No TV licence required except for content on BBC iPlayer.
Futurelearn
Free to access 100s of courses, only pay to upgrade if you need a certificate in your name (own account from age 14+ but younger learners can use a parent account).
Seneca
https://www.senecalearning.com
For those revising at GCSE or A level. Tons of free revision content. Paid access to higher level material.
Blockly
Learn computer programming skills - fun and free.
Scratch
https://scratch.mit.edu/explore/projects/games/
Creative computer programming
National Geographic Kids
https://www.natgeokids.com/uk/
Activities and quizzes for younger kids.
Duolingo
Learn languages for free. Web or app.
Mystery Science
Free science lessons
The Kids Should See This
https://thekidshouldseethis.com
Wide range of cool educational videos
Crash Course Kids
https://m.youtube.com/user/crashcoursekids
As above for a younger audience
Crest Awards
Science awards you can complete from home.
iDEA Awards
Digital enterprise award scheme you can complete online.
Paw Print Badges
https://www.pawprintbadges.co.uk
Free challenge packs and other downloads. Many activities can be completed indoors. Badges cost but are optional.
Tinkercad
All kinds of making.
Prodigy Maths
Is in U.S. grades, but good for UK Primary age.
Cbeebies Radio
https://www.bbc.co.uk/cbeebies/radio
Listening activities for the younger ones.
Nature Detectives
https://naturedetectives.woodlandtrust.org.uk/naturedetectives/
A lot of these can be done in a garden, or if you can get to a remote forest location!
Oxford Owl for Home
https://www.oxfordowl.co.uk/for-home/
Lots of free resources for Primary age
Geography Games
https://world-geography-games.com/world.html
Geography gaming!
Red Ted Art
Easy arts and crafts for little ones
The Imagination Tree
https://theimaginationtree.com
Creative art and craft activities for the very youngest.
Toy Theater
Educational online games