A C++ template library for efficient forward-time population genetic   simulation of large populations
  fwdpp is a C++ library of routines intended to facilitate the development of forward-time simulations under arbitrary mutation and fitness models. The library design provides a combination of speed, low memory overhead, and modeling flexibility not currently available from other forward simulation tools. The library is particularly useful when the simulation of large populations is required, as programs implemented using the library are much more efficient that other available forward simulation programs. 
Kevin R. Thornton
q-bio.PE