Excellent general crossword sites
UKpuzzle.com offers a wealth of free crosswords by professional setter Anax, a member of The Times cryptic team who also makes regular appearances on Alberich's site (below). There is also a non-cryptic service available for monthly trade magazines.
Cryptica John Halpern aka Paul is one of the favourite setters of Cryptics.co.uk.  He is on a mission to give cryptic crosswords (the one thing we Brits definitely do better than anyone else in the world) the sort of high profile they deserve.  We strongly recommend a visit to his brand new website that is destined to succeed in putting FUN into what is often - wrongly - imagined to be a staid and arcane world.
Free Crosswords Online     Printable cryptic crosswords by Alberich, a professional compiler, plus a showcase of puzzles by new compilers. There's also a substantial section offering useful advice and information for would-be professional compilers.
Daily Telegraph Crosswords (subscription site)    We like the Telegraph crossword here at Cryptics.co.uk.  Check out our daily solvers guide on the forum.

           
Crossword solving help
Dictionary.com    Lost your Chambers?  Try this excellent online dictionary and thesaurus service.
One Across    Extremely useful word search facility.
Wordsmith.org    The best anagram site on the interweb.

Non crossword stuff we like
Ambernectar    For people who like Hull City and beer (and swearing!).  See if you can spot Jim wasting time on the forums.

If you have any suggestions for sites we could link, or want to link your own site, email Jim at Jim@Cryptics.co.uk