Fiction
Escape Pod, the science fiction podcast magazine. http://escapepod.org/
PodCastle, the fantasy fiction podcast. http://podcastle.org/
Science
The PBS Space Time channel on YouTube
Isaac Arthur’s channel on YouTube
Education
The Open Textbook Library with the University of Minnesota.
Artists
Abiogenisis’s deviantART gallery, where you can find beautiful paintings of imagined life on other planets.