NBII Image Gallery
What is metadata? - Metadata is simply data about data.
Metadata can be structured or unstructured and is often used to describe, summarize, and/or aid in the human and/or machine process of information.
FGDC Biological Data Profile - describing and documenting datasets
Dublin Core+ - describing and documenting web-sites, images, publications, and other web resources
Darwin Core - digitizing and sharing of collection information
Open GIS - in support of sharing, registering, and interoperability of geospatial data layers.