Extra U(1) gauge groups and axion-like particles are among the most popular extensions of the Standard Model. They are very well motivated from string theory and have interesting phenomenological applications. In this talk I will describe how these ingredients can be used to probe hidden sectors in which, e.g. Dark Matter and/or SUSY breaking could reside. I will focus in particular on models with millicharged Dark Matter and Z’ mediation, and construct explicit D-brane setups where these elements arise. I will briefly discuss some theoretical constraints and particular phenomenological features of these constructions.