Graphserver provides fast shortest-path computations on very large graphs, for use as a sub-component of a trip-planning service.
IVYGIS is a yet another take on getting PostGIS working with Ruby on Rails. It consists of building tools for building database-backed, web-based presentation of geographic data in form of maps, with mouse-sensitive polygons, line-strings, and the like.
Extension library for Ruby to decode/encode WMO GRIB messages.
weatherdb makes weather data accessible from geographers: it maintains real-time MySQL databases of meteorological data retrieved from the Web and Unidata LDM, and provides CGI for catalog and OGC Web Map Service.