Armadillo is a C++ template library to do linear algebra. It tries to provide an API that is similar to Matlab, so its pretty easy to use. It has a SVD implementation that is built upon LAPACK and BLAS. Usage is simple:
#include
// Input matrix of type float
arma::fmat inMat;
// Output matrices
arma::fmat U;
arma::fvec S;
arma::fmat V;
// Perform SVD
arma::svd(U, S, V, inMat);