I will discuss the real-time dynamics of interacting electrons that are described by Hubbard-type models. This is of interest to describe the electronic relaxation on femtosecond timescales in pump-probe experiments on strongly correlated materials, and can also apply to experiments with cold atomic gases. In both situations an essentially isolated quantum-mechanical many-body system is forced out of equilibrium and relaxes to a new stationary state, which is not necessarily the thermal state predicted by statistical mechanics. I will discuss how nonequilibrium Green functions for Hubbard-type models can be obtained using dynamical mean-field theory, and how they are related to time-resolved photoemission and optical spectra.