Opportunistic networks may be employed for communication in places where there is no previous infrastructure, or the existing infrastructure has been rendered unusable. Emergency networks for calamity mitigation are an example in which mobile devices are used to form an opportunistic network. An important feature of such networks is physical and logical resource location. Further, this functionality should be tolerant to disruptions and long delays due to frequent node connections/disconnections and unpredictable mobility. This paper proposes and evaluates the performance of resource location algorithms for opportunistic networks. Simulation results show that the proposed solutions increase the discovery rate by up to 80%, because our extensions are more adapted to the specific characteristics of resource discovery, as well as due to the use of proactive resource announcement.