Open Source Cloud Map
This map requires no login but does not allow you to create your own custom map by adding or removing map layers. It contains all layers provided by the GeoServer map server and also several Bing Map base layers. This map uses the EPSG 900913 ('Spherical Mercator') spatial reference, which is commonly used by commercial providers such as Google Maps®, Microsoft Virtual Earth® (Bing Maps®), Yahoo Maps®, etc.
The customizable map includes tools to add additional layers from other map servers on the web. It requires a login in order to identify you for retrieving and saving your own custom map. It uses the EPSG:4326 (latitude/longitude based on the WGS84 datum) spatial reference. This is the most widely supported spatial reference system for non commercial providers and makes it possible to add layers from these providers to the map.
An introduction to the map application.
A complete user guide for both maps.
To help you get started, follow this step by step tutorial for creating a custom map.
A technical description of the system design.
Documentation describing how to set up a similar system.