Polymeric nanofiber non-woven materials produced by electrospinning have extremely high surface-to-mass (or volume) ratio and a porous structure with excellent pore-interconnectivity. These characteristics plus the functionalities and surface chemistry of the polymer itself impart the nano-fibers with desirable properties for a range of advanced applications. This review summarizes the recent progress in electrospun nanofibers, with an emphasis on their applications.