GeoServer is a fully functional open source WFS-T and WMS server that follows the OGC open standards.
With Geoserver you can publish data as maps/images (using the WMS), as actual data (using the WFS), and allow users to update, delete, and insert features (using the WFS-T), utilizing a variety of backend spatial data formats (PostGIS, Shapefile, Oracle, ArcSDE, DB2 and more).
GeoServer’s focus is ease of use and support for open standards in order to enable anyone to quickly share their geospatial information in an interoperable way.