Crossed complexes and homotopy groupoids as non commutative tools for   higher dimensional local-to-global problems
  We outline the main features of the definitions and applications of crossed complexes and cubical $\omega$-groupoids with connections. These give forms of higher homotopy groupoids, and new views of basic algebraic topology and the cohomology of groups, with the ability to obtain some non commutative results and compute some homotopy types. 
Ronald Brown