Reading:
Epic https://www.getepic.com/
A-Z Reading https://www.readinga-z.com/
Abcmouse.com https://www.abcmouse.com/
Abcya.com https://www.abcya.com/
Starfall.com https://www.starfall.com/h/
Khanacademy https://www.khanacademy.org/
Audible https://www.audible.com/
Brainpopjr https://jr.brainpop.com/
PBSkids https://pbskids.org/
Spelling/vocabulary/writing:
Spelling City https://www.spellingcity.com/
Math:
IXL math https://www.ixl.com/math/
Xtra Math https://xtramath.org/#/home/index
Prodigy.com https://www.prodigygame.com/
Soft schools https://www.softschools.com/
Science/Social Studies:
Scholastic https://classroommagazines.scholastic.com/support/learnathome.html
Virtual Field Trips: (these will take you to sites with multiple recommendations)
We Are Teachers https://www.weareteachers.com/best-virtual-field-trips/
Virtual Museums https://www.educatorstechnology.com/2014/01/20-wonderful-online-museums-and-sites.html