An open source python application that exposes data stores, e.g., HDF and NetCDF Files, in the web way.
It makes file inner components, such attributes and data arrays, directly addressable and accessible via well-defined and meaningful URLs.
It can be installed as a command line tool and/or a RESTful web service.

So I think whatever eats PHP’s lunch is going to be a standardised programming environment rather than a mere language by itself – one that might conceivably even be lanugage-agnostic, though in that case platform features among participating languages will likely have to be reasonably similar. An example of what I am thinking of might be Google’s App Engine.

Tagzania is about tags and places. If you register and log in, you can add places, points, to create and document your maps.

Rhizome is a Wiki-like content management and delivery system that exposes the entire site -- content, structure, and metadata as editable RDF.