University of California
University of California Berkeley: Classifying Galaxies
Find out how galaxies are classified and then see if you can apply that knowledge to identify the different types of galaxies. In addition to explaining Hubble's galaxy classification system, the site has links to Hubble Space Telescope...
Other
Sloan Digital Sky Survey: Galaxy Zoo
Explore the universe like you have never seen it. Take part in classifying images of galaxies taken from the Hubble telescope archives. This is a crowdsourced scientific research project.
NASA
Nasa: Imagine the Universe: Active Galaxies and Quasars
Describes quasars as being classified within the category of an active galaxy. A description of the emergence of high-energy. Definitions of key words are provided.gamma-ray quasars as an important component of the gamma-ray sky.
Space Telescope Science Institute
Amazing Space: Hubble Deep Field Academy
At this site, students can become a Steller Statistician, Cosmic Classifier, Galactic Guide or a Universal Graduate by attending the Hubble Deep Field Academy--and entering information in their Hubble Academy Log (HAL), which is assessed...