In recent years, large-scale sensor arrays and the vast datasets they produce worldwide are being utilized, shared, and published by a rising number of researchers on an ever-increasing frequency. Examples include the global-scale Argos network of buoys, the weather networks of the World Meteorological Organization, and the global GPS zenith total delay (ZTD) observation network. Significant amount of efforts (e.g., GEOSS and NOAA IOOS) have been put forth to web-enable these large-scale sensor networks so that the sensors and their data can be accessible through interoperable sensor web standards. Moreover, with the advent of the low-cost sensor networks and data loggers, it is technologically and economically feasible for individual scientists to deploy and operate small- to medium-scale sensor arrays at strategic locations for their own research purposes. There is a spectrum of sensor networks ranging from local-scale short-term sensor arrays to global-scale permanent observatories. The vision of the worldwide sensor web is becoming a reality.