NCBI

Please note that there is a tutorial about this.

Starting with an organism or taxon name...

1. Search the Taxonomy database with the organism name. Accepted common names usually work at all taxonomic levels. Use the scientific name or formal name if no results are obtained with the common name.
2. Click on the desired taxon name in the results. For terminal taxa - generally subspecies, species, or strains - this link leads directly to the summary page. For higher taxa this link will lead to the Taxonomy Browser showing the lower taxa contained within the higher taxon.
3. If necessary, click on the desired taxon link in the Taxonomy Browser to reach the summary page.
4. The number of records in each database are linked in the Entrez records table on the taxon summary page . Click the linked number of records in the table to retrieve all records from the chosen sequence database (Nucleotide, Nucleotide EST, Nucleotide GSS, Protein).