www.crossword.org.uk - The Crossword Centre has regular monthly puzzles, some very informative articles and an excellent message board
www.fifteensquared.net - A daily blog giving a breakdown of Guardian, FT and Independent puzzles - very useful if you do these puzzles and get stuck!
www.ukpuzzle.com/phpBB3/index.php - A cryptic clue writing contest hosted by Anax, a professional setter
www.bigdave44.com - Big Dave's crossword blog, which reviews the Telegraph puzzles daily, and in addition has a collection of puzzles
www.phionline.net.nz - The site of Paul Henderson, AKA Phi. It contains a collection of his crosswords and several crossword-related articles.
www.mycrossword.co.uk - A website that enables users to create and publish their own crosswords for others to enjoy.