PUBMED
NLM's search service to access the 9 million citations in MEDLINE and Pre-MEDLINE (with links to participating on-line journals), and other related databases.
Bio-Mirror
This is a world bioinformatic public service for high-speed access to up-to-date DNA & protein biological sequence databanks.
National Center for Biotechnology Information
Resources available from NCBI include PubMed, GenBank (nucleotide and protein sequence databases), gene taxonomy database, 3D structural databases, OMIM (a human genetic database), human genome resources and many others.
BioTech
Associated with the University of Texas and the University of Indiana, this site includes great science resources with excellent annotations. Aimed at everyone from high school students to professional researchers.