BLAST (Basic Local Alignment Search Tool) is a set of sequence similarity search programs. Giving a query sequence (nucelotide or protein), BLAST searches a user specified database for similar sequences.
Query Database Blast Program Note
nucleotide nucleotide blastn
protein protein blastp
protein protein psi- and phi-blastp increased sensitivity
nucleotide protein blastx query translated into protein
nucleotide nucleotide database tranlated tblastx query translated into protein
protein nucleotide database tranlated tblastn

Blast web server can be found at NCBI BLAST ( Detailed instructions on how to use BLAST can be found at the NCBI site.

If you prefer results returned to you by email, you may use Wu-Blast server at European Bioinformatics Institute (