The power consumption of ICT is still increasing. To date it is not clear if the energy savings through ICT overbalance the energy consumption by ICT or not. Where manifold efforts of Green IT address the environmental aspects of sustainability considering computer hardware, there is a lack of models, descriptions, or realizations in the area of computer software. In this paper we present some results that form the basis towards a definition of the term "Sustainable Software", an outline of a process and lifecycle model for "Green and Sustainable Software Engineering", and six concrete instances of this model for practitioners.