The Khan Academy has some incredible courses in Maths and Science (and more!) to support students all the way from Kindergarten to college/university level! I found their course on Multivariate Calculus (https://www.khanacademy.org/math/multivariable-calculus) incredibly useful during the second year of my Physics undergraduate course. I only wish I had known about the site sooner!
https://europeanastrobiology.eu/streamed-seminars/
Weekly/biweekly online seminars
On everything related to astrobiology - Earth climate science, evolution, planetary science, geology, biology, exoplanets and more
https://discussions.rockyworlds.org/
Monthly virtual meeting series
On topics related to rocky planets
https://www.schoolsobservatory.org/
The National Schools Observatory (NSO) provides resources (including telescope time!), technical support, and classes to bring "astronomy into the classroom – supporting schools to take hundreds of thousands of observations of the cosmos. Engaging millions of people with space education over the last 15+ years."
University of Liverpool / Liverpool John Moores University
Here is a list of online resources that are helpful for the University of Liverpool and Liverpool John Moores University course in Computational Astrophysics (PHYS216), which I came across while assisting in teaching the module between 2021 and 2024. Students, as well as using your lecture notes, please remember that you are allowed to Google things! It is best if your citations are from published papers, but using websites to help you understand the physics is a great idea (even Wikipedia)!
NGC 4151, captured by the Hubble Space Telescope’s Wide Field Camera 3. When you open the photometric image of NGC4151 (NGC4151_SSDSS_r.fits) with Gaia, try using a logarithmic colour scale, and you should be able to see the galaxy spiral arms too!