Science.gov searches over 60 databases and over 2,200 scientific websites to provide users with access to more than 200 million pages of authoritative federal science information including research and development results.
Huge collection of resources for students and teachers of biology. Search for a specific topic or browse to see what's available. You can also see the material arranged by scholarly level, from elementary to graduate.
Overview of the many areas that Biology covers, such as cellular biology, microbiology, etc. Good site to gain general information. There is also a section on careers and an extensive glossary of bioscience terms.
Collections of many sources on major issues in biology, such as biodiversity, evolution, genetics, etc. Good place to start a research project. The "Topic Directory" in the left margin is a good starting point. From the American Institute of Biological Sciences.