Dicyclohexylcarbodiimide (DCC) has the following structure:

 __         __
/  \       /  \
\__/\     /\__/
This molecule is the most general reagent for the formation of peptide bonds, which are the connecting bonds in polypeptides between amino acids. The mechanism of formation of the peptide bond is, the amino acid (or polypeptide) with a deprotected C-terminus attacks the carbon in the DCC, forming an O-acyl isourea. The structure is the same as the structure above, except one of the C=N double bonds is moved to the oxygen of the C-terminus of the amino acid or polypeptide. All that happens as a result is, the C-terminus is more reactive, and so the formation of the peptide bond is made possible. The DCC is then kicked off, but as an N,N'-dicyclohexyl urea.

I'm not sure where to go for better information on DCC, but for more information on polypeptide synthesis in general, refer to the polypeptide node. This information is derived from synthesis of information presented in Organic Chemistry: Structure and Function by Vollhardt and Schore, and lectures given by Professor Eric T. Kool at Stanford Uniiversity.