Distributed sensor networks operating through wireless communication offer a powerful means to sense, analyze and respond to dynamic environments spread over vast areas. Latest developments in micro electro mechanical sensors (MEMS) and related devices offer several technical and operational advantages making distributed sensor networks as a viable approach. Robustly packaged, inexpensive, energy aware and tamper proof sensors deployed in massively as an ad-hoc wireless sensor network add a whole new dimension to several high impact applications such as air port surveillance, traffic monitoring, environmental monitoring, surveillance against bio-terrorism, battle field damage assessment etc. In short they permit pervasive, persistent and high endurance monitoring of hostile environments. This paper is an introduction to some of the exciting information processing problems that are being solved to effectively harvest the benefits of current and emerging nano, micro, and macro sensors in distributed sensor networks.