GIS/RS Data Services

Information that describes the GIS item is called metadata. The metadata can give info about the content, quality, condition, origin, and other characteristics of data. A good metadata for the spatial data may describe and document its subject matter; how, when, where, and by whom the data was collected; availability and distribution information; its projection, scale, resolution, and accuracy; and its reliability with regard to some standard. When care is taken to provide good descriptions, you can find appropriate items with a search and evaluate which of the items in your search results is the correct one to use.

Federal Geographic Data Committee
The Federal Geographic Data Committee (FGDC) in cooperation with state, local and tribal governments, private sector and academic community gives some guidance on the geospatial data standards for implementing the National Spatial Data Infrastructure. The FGDC is committed to using voluntary consensus standards, such as those developed through ISO and ANSI. 

USGS Metadata Tool Page
Lists some metadata tools for download that comply with FGDC standards.