I'm trying to get an idea what web services exist for doing geometry operations. I know that Esri's GeometryService supports several operations, but does anything else exist? I've started a very simple project built on JTS and Google App Engine to support a Code for America project an am trying to decide if I should build it out or not. Any thoughts?
The best RESTful GIS implementation I have seen so far is Open Source: FeatureServer It is a true RESTful implementation, meaning that it really uses HTTP methods to offer CRUD methods for geographic objects.
It offers many kind of storage, including PostGis, and it is very easy to use it from within OpenLayers.
Keep in mind that if you are going to choose for a RESTful implementation, you are not going to use the OGC standards (WFS and REST are not friends): this can not be an option in many cases.