Primer designing tools

Primer3 is a free online tool to design and analyze primers for PCR and real time PCR experiments.

2. Fast PCR:
FastPCR is an integrated tool for PCR primers or probe design, in silico PCR, oligonucleotide assembly and analyses, alignment and repeat searching. This is downloadable.

AutoPrime allows to rapidly design primers for real-time PCR measurement of eukaryotic expression.

Genefisher 2 is an interactive web-based program for designing degenerate primers. The procedure leads to isolation of genes in a target organism using multiple alignments of related genes from different organisms. The term "gene fishing" refers to the technique where PCR is used to isolate a postulated but unknown target sequence from a pool of DNA.

5. Primer BLAST: 
Extensively used for designing primer and checking the specificity of a given primer.