Chess Problem Composition Sites
British Chess Problem Society-publisher of the fine magazine "The Problemist".
British Chess Solving Championship-See all the latest details plus much more on the chess problem scene at Brian Stephensons site.
Permanent Commission of the FIDE for Chess Composition-official FIDE site for all aspects of chess composition.
Problemesis- magazine and competitions.
Public Domain Chess Composition Books-several collections of chess problems from old masters in free books (.pdf format)