new Polyglot 1.4w24 at Fonzy's site

Fonzy Bluemers and friends continue to develop and bugfix my favorite UCI-to-WB adaptor.
Thanks to them.

Computer Chess Club archives

A searchable archive of all Computer Chess Club posts before its migration to a phpBB forum in march 2006.
http://www.stmintz.com/ccc/index.php

Real-time viewing of chess engine's "thinking"

http://turbulence.org/spotlight/thinking/chess.html

The underlying engine does not seem to play strong chess but real-time animated plotting of its thinking is quite fascinating to watch.

ChessPub Openings forum

http://www.chesspub.com/cgi-bin/yabb2/YaBB.pl
One of the best ressources on the web with discussions on current chess opening theory trends.
Several grandmasters are regular contributors with original analyses.

Chess openings theory at Kenilworth Chess Club

Michael Goeller maintains a most interesting page of hundreds (!) of categorised links to chess opening theory sites here : http://www.kenilworthchessclub.org/links/openings.html .
Quite a few interesting opening theory articles are hosted at his club's site :
http://www.kenilworthchessclub.org/articles/index.html
Michael himself contributed quite a few of the best among these ones.
He also regularly updates a blog with many interesting analyses :
http://www.kenilworthchessclub.org/kenilworthian/

ChessX 0.6 PGN database has just been released ...

... two years after last version.
Still not really a full-fledged chess database, but yet an interesting multi-platform PGN viewer and editor.