The slow non-equilibrium dynamics in various systems show common physical aging features and sometimes surprising rejuvenation and memory effects. We present two theoretical approaches to understand these phenomena on the basis of coarse grained models. In the first approach a system in configuration space is considered that changes its state by thermally activated jumps in a random energy landscape. In the second approach an effective dynamics for the Edwards-Anderson spin-glass model on a hierarchical lattice is studied by means of real-space renormalization concepts.