Geospatial Mashup Components
When Howard announced his projection web service, I told him that this was not nearly as useful as a service that operates on entire documents. A service that reprojected, buffered, or spatially aggregated the items in a GeoRSS feed or KML document could be a great component in a mashup pipeline. Pipes doesn't support remote modules yet, but I expect that's only a matter of time. It's an obvious next step.