GRDDL is a technique for using XML/XHTML dialects as CustomRdfDialects.
Implementations of the core GRDDL algorithm that participate in test result reporting in the GRDDL working group:
redland by Dave Beckett has fairly complete GRDDL support as of release 4.14, released 31 Jan 2007.
A GRDDL Reader for Jena noted in a 20 Jan 2007 comment from Jeremy Carroll
GRDDL.py based on 4suite; by Chimezie Ogbuji 10 Nov 2006 with contributions from DanConnolly and JohnClark
Virtuoso's in-built RDF Middleware ("Sponger") as per V5.0 release on 04-10-2007
Other implementations, possibly ongoing:
grddljs, Dan Connolly's Javascript implementation started around Aug 2007
Swignition includes mostly complete support for GRDDL as of Jan 2009. Supports transformations in XSLT1 and RDF-EASE. Planned support for ECMAScript transformations.
Support in TopBraid Composer was originally announced Tuesday, November 07, 2006 by Holger Knublauch. In a July 2007 update, Holger says they plan to replace their implementation with the GRDDL Reader for Jena.
These seem to be less actively maintained:
grddler.sh by Sean B. Palmer, released 09 Jun 2006
GRDDL parser for PHP announced 2 Nov 2004 by Chris Bizer
Applications:
The Semantic Web Client Library allows SPARQL queries over RDF/XML and GRDDL data sources. The GRDDL support is based on Jeremy's library.
a Greasemonkey script allows to load RDF data from XHTML pages. by Alf Eaton, script Last-Modified 23 Aug 2005 22:10:37 GMT; announced the next day.
OpenLink Data Explorer (ODE), Web browser plug-in version (Firefox only, so far), rides atop the Virtuoso Sponger (configurable to use other GRDDLers).
Online services:
triplr by Dave Beckett. (announced when?)
The Redland Raptor RDF Parser Demonstration supports some GRDDL since 04 Apr 2005
online GRDDL demo, implemented by Dominique Hazaël-Massieux on top of W3C's XSLT service, announced 24 Nov 2003
OpenLink Data Explorer (ODE), server-side version, rides atop the Virtuoso Sponger (configurable to use other GRDDLers).