HHMI Beautiful Biology offers images, videos, and more of the microscopic world of biology.
iBiology: Free biology videos, courses, and educational resources from Science Communication Lab
OneZoom Tree of Life Explorer, "an interactive map of the evolutionary links between all living things known to science."
Smithsonian Ocean provides articles, slideshows, and more on the world's oceans.
Vision Learning: Biology provides high-quality, accessible, educational material in the STEM disciplines; includes a Library of Learning modules and a glossary.
Web Anatomy Self Test from University of Minnesota offers several practice tests, including medical terminology.