StrataScutter is a project mainly written in D and JAVASCRIPT, it's free.
Scutter RDF crawler using Stratified Javascript
This is an experimental FOAF / Linked Data crawler, written using the stratified Javascript libraries from http://onilabs.com/apollo and the RDF utilities from http://dig.csail.mit.edu/2007/tab/
Use at own risk, etc.
Status: it can fetch a bunch of RDF files in pseudo-parallel, and parse / process them on arrival. Currently it doesn't do anything with the results except update an HTML dashboard.
Ultimately it should support also RDFa, microformats, Turtle etc; for now the parsing is wired to expect rdf/xml.
See notes in the code for details.