We have selected University of Arizona Biology Project as the world's very best website on Biology.
The University of Arizona Biology Project website is an interactive online resource for teaching biology at high school and college level. It is also aimed at medical students, physicians, writers on science, and the interested general public.
The website is organized in eight main sections covering: Biochemistry, Cell Biology, Chemicals & Human Health, Developmental Biology, Human Biology, Immunology, Mendelian Genetics, and Molecular Biology. For each section there is are Problem Sets & Tutorials, and also Activities. Several of the sections are available in Spanish and Portuguese translation.
For example, the Biochemistry section Problem Sets & Tutorials covers topics including: Acids & Bases, B12/Folate, Carbohydrate Metabolism Regulation, Chemistry, Clinical Correlates of pH levels, Energy, Enzymes & Catalysis, Large Molecules, Metabolism, Photosynthesis 1, Photosynthesis 2, and the Chemistry of Amino Acids.
Click here for the 'University of Arizona Biology Project': http://www.biology.arizona.edu/