geomorphometry.org

DTM SlopeMap built using the ArcGIS JavaScript API. The ESRI's World Elevation Services became available in early 2012. There are image services, data download services, and analysis task services available, as well as sample applications.

The services are built from a collection of data sources, ranging from less than a meter resolution up to almost 5 kilometers, and includes services of elevation, shaded relief, slope, and aspect. Read more about the ESRI's elevation services and hydro services in this blog post.