Major research resources:
[http://ncbi.nlm.nih.gov/ NCBI] - Home of the human genome project data and many other molecular databases (U.S. National Center for Biotechnology Information)
[http://pubmed.gov PubMed] - Search biomedical science abstracts. The place to find journal articles.
[http://portal.isiknowledge.com ISI Web of Science] - Find out who cited a journal article. Useful for finding related articles.
[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=books NCBI Bookshelf] - Many biology related text books fully searchable online.