This article gives a short review on the convergence of collocation methods for Volterra integral equations of the second kind and extends some recent results on iterated collocation to nonlinear problems. But the main goal of this paper is the implementation of collocation and iterated collocation methods. Subjects like error estimation (local and global), stepsize strategy and approximation of the lag-term are discussed, and implemented in a FORTRAN code COLVI2. Several numerical examples demonstrate the good performance of this code. Comparisons with other existing codes are included.