This report is based on the 2004 AGU Fall Meeting's session entitled Special Focusc Advances in Data Acquisition, Management, Analysis and Displayc Cyberinfrastructure for Earth Systems Science IVc Sensor Networks. An environmental sensor network comprises an array of sensors that gather data autonomously and automatically forward the data to a central server. What differentiates modern sensor networks from previous techniques is an emphasis on intelligence in the sensor packages as well as the data network. Modern sensor networks also typically publish the data on the server to the World Wide Web and allow real-time access to the data. These networks require a unique combination of technological and environmental understanding, and have the potential of creating a revolution in environmental monitoring, similar in impact to satellite remote sensing in the 1970s.