Advancements in wireless sensor networks (WSN) over the past two decades has foreseen an increased interest in the potential use in applications like combat field, security surveillance, border protection, disaster management and reconnaissance. Moreover, researchers have termed the 21st century as the "Sensor Decade" [3]. Sensor nodes are remotely deployed in large numbers and expected to operate autonomously in harsh environments. Now-a-days routing protocols are being designed, where energy awareness is an essential designing issue. In this paper, survey on recent routing protocols for sensor networks along with their classification and approaches is done . Each routing protocol is described under the appropriate category followed by possible future research areas.