GeoServer is an open source software server written in Java that allows users to share and edit geospatial data.
"... Designed for interoperability, it publishes data from any major spatial data source using open standards." (http://geoserver.org).
GeoServer is the reference implementation of the Open Geospatial Consortium (OGC) Web Feature Service (WFS) and Web Coverage Service (WCS) standards, as well as a high performance certified compliant Web Map Service (WMS). GeoServer forms a core component of the Geospatial Web.
See http://geoserver.org for more details and downloads.