If the Moon Were Only 1 Pixel is a tediously accurate model of the Solar System that Josh Worth made to explain to his daughter just how difficult it is to go on holiday to Mars.
The Habitable Exoplanets Catalog is a database of the planets outside our solar system which are considered the most suitable for life according to certain steps and metrics. So far 16 have been identified as possible candidates. This Guardian article is a good introduction. You can also just dive into the catalogue, which ranks planets on two main scales, similarity to Earth and surface habitability (note that all images are computer renderings). The catalog is a project of the Planetary Habitability Laboratory at University of Puerto Rico in Arecibo (home to the world's largest radiotelescope).
Andreas Cellarius was a scholar of the 17th Century who produced one of the most famous cosmological atlases of all time, Harmonia Macrocosmica, featuring 29 beautiful plates (large, high-quality scans), illustrating various aspects of the Universe as understood by the Western science of his time. It's impossible to pick favorites among them, but here are three examples: Phases of the Moon, Sizes of the Celestial Bodies and Stars and Constellations of the Northern Sky.
Cosmic Journeys is a documentary series on various astronomical and space-related subjects, e.g. supermassive black holes, Apollo 12, whether the universe is infinite and many more. The creators, SpaceRip have a lot of other, shorter videos online as well. They are indexed here. Most, if not all, of the videos are available in HD.
UniverseNewsFilter: Scientists claim to have detected dark matter! Here are NASA's press release, feature page and multimedia presentation. For an explanation what dark matter is, I refer you to this page. After all that excitement, you can sit down and work out how much dark matter is in the Milky Way.