Mike Bergman's site has an interesting article on ESW, titled "Enterprise Semantic Webs (ESW) Demand New Database Paradigms", at http://www.mkbergman.com/?p=185. In fact, it's one of the few defintions of ESW availible.

Link to BB.COM SOA Subject

Mike Bergman has written numerous insightful articles about the Semantic Web.

From the W3.Org site

The Open Data Movement aims at making data freely available to everyone. There are already various interesting open data sources availiable on the Web.

Updated Sept 24 2008: added features and SWCL link

REWERSE is short for "Reasoning on the Web with Rules and Semantics".

From the site: REWERSE is a research "Network of Excellence" (NoE) on "Reasoning on the Web" that is funded by the EU Commission and Switzerland within the "6th Framework Programme" (FP6), Information Society Technologies (IST), Priority 2 under the project reference number 506779. REWERSE addresses the IST strategic action line "Semantic-based knowledge systems".

Link to the LSDIS (Large Scale Distributed Information Systems) Lab

From the site:

The Semantic Web Client Library represents the complete Semantic Web as a single RDF graph. The library enables applications to query this global graph using SPARQL- and find(SPO) queries. To answer queries, the library dynamically retrieves information from the Semantic Web by dereferencing HTTP URIs and by following rdfs:seeAlso links. The library is written in Java and is based on the Jena framework.

SemSol seems to be connected to the Semantic Web Community Portal, http://www.semanticweb.org/, which has been on the verge of being relauched for many months ....

From the SemSol site, "SemSol is a forthcoming Web development framework that uses Semantic Web technology to significantly increase productivity and flexibility for everyday Web programming".

Also see http://bnode.org/, Benjamin Nowack's personal website.

Updated Sept 25 2008: new link This page describes the taxonomy of semantic web topics adopted by the European projects Knowledge Web and REWERSE

Semantic web tutorial ( Static HTML ).

Update 3/26/2008 - ARC completely reimplemented and released as ARC2.

Update 7/25/2008 - added Triplify 0.3 section.

From the ARC site:

ARC is a lightweight, SPARQL-enabled RDF system for mainstream Web projects. It is written in PHP and has been optimized for shared (or otherwise performance- or privilege-limited) Web environments.

ARC facilitates the integration of RDF and SPARQL functionality in PHP/MySQL-driven frameworks.

From the site:

SemWebCentral is an Open Source development web site for the Semantic Web. It was established in January, 2004 to support the Semantic Web community by providing a free, centralized place for Open Source developers to manage Semantic Web software and content development. Another purpose is to provide resources for developers or other interested parties to learn about the Semantic Web and how to begin developing Semantic Web content and software.

The Inference Web is a Semantic Web based knowledge provenance infrastructure that supports interoperable explanations of sources, assumptions, learned information, and answers as an enabler for trust.

Tools for Semantic Web Rules and Ontologies, including Translation, Inferencing, Analysis, and Authoring.

From the site:

The Semantic Web Education and Outreach (SWEO) Interest Group has been established to develop strategies and materials to increase awareness among the Web community of the need and benefit for the Semantic Web, and educate the Web community regarding related solutions and technologies. 

A very concise and straightforward introduction to XML, RDF and the Semantic Web.

Updated Sept 7 2008: added seaBreeze link

Seaside

To get a good feel for Seaside development environment, read the excellent technical introduction by Shaffer Consulting.

Note that the article was written in 2005 and may be obsolete in parts. For example, Seaside now supports several object-oriented databases, including Gemstone.

Revised Nov 1 2008: Draft of OWL2 specs.

The recent drafts of the OWL2 specification describe some important changes from OWL1. In a nutshell,

The structural specification of OWL 2 provides the foundation for the implementation of OWL 2 tools such as APIs and reasoners. ... This document also defines the functional-style syntax, which closely follows the structural specification and allows OWL 2 ontologies to be written in a compact form.

The main link is to Oracle - Semantic Technologies Center. so far .... From the site:

Semantic Technologies are designed to extend the capabilities of information on the Web and enterprise systems to be networked in meaningful ways. ... Oracle Spatial 11g introduces the industry's first open, scalable, secure and reliable RDF management platform. Based on a graph data model, RDF triples are persisted, indexed and queried, similar to other object-relational data types.

From the About CSAIL page:

The primary mission of CSAIL ( Computer Science and Artificial Intelligence Laboratory ) is research in both computation and artificial intelligence, broadly construed. It is organized into four broad research areas:

Systems covers all aspects of the building of both hardware and software computational systems

Perception and Learning includes work on the sorts of things that all people manage to do effortlessly, both emulating those abilities, and simulating their appearance.

From the drupal.org post, Semantic Search - Faceted Search and Semantic Web:

It's getting serious. Things are moving resolutely forward toward Drupal 6 and 7.

The seems to be some confusion about the difference between 'rule engines' and 'semantic web' applications.  See related link to "Semantic Web Inferencing versus Rule Engines"

OntoGrid provides a technical infrastructure for the rapid prototyping and development of knowledge-intensive services for the Semantic Grid.

Jan 26 2009. derived from PHP Wikis and Knowledge Wikis.

Often referred to as "knowledge wikis", they are capable of providing some level of knowledge representation and management functions as well as the usual features available in traditional wikis. They may be the closest existing solution to some of the requirements for a Semantic Web ( however it gets defined ).

Nov 4 2009: Getting active, or maybe reactivating.

This page is just a collection of links so far. The link above for the 'Miscellaneous' subject is to my own modest effort with Semantic Mediawiki.  It's nascent but coming along.

The entire Semantic Web subject area will be getting a makeover soon.

Weaving Meaning: An Overview of the Semantic Web

Good W3 Powerpoint presentation by Eric Miller.

The Semantic Web held pride of place at the AAAI 2008 Spring Symposium Series.

This is a new topic ... it is more abstract than most content on this site and may be moved to the Home site.

Of the 702 Semantic Web tools listed in Mike Bergman's masterlist, 332 are implmented in Java .... and Java now being a fully open source and open licence language ...

Stray link I'll find a home for: http://www.daml.org/tools/

SWCL - Semantic Web Client Library:

Updated Sept 16 2008

Semantic web search engines ? Social bookmarking run mad ? We shall see. The new search technology is still early in the S-curve and more useful for pop culture subjects than for rule based systems.

From the WikiaSearch project page:

Wikia's search engine concept is that of trusted user feedback from a community of users acting together in an open, transparent, public way.