A good way to get involved (in North America) is to join the National Scrabble Association (NSA); a registration form comes with every new Scrabble set.
Verbalobe -- a community portal for players of competitive Scrabble worldwide -- Verbalobe.com is a free site offered to players of Scrabble and other word games -- from novice to expert -- who wish to improve their ability and performance through learning more words. Strategy and other aspects of gameplay are covered, too. Members are invited to actively participate in forums, and submit lists, links, downloads, and original articles of timely or lasting value.
Ben Loiterstein's Scrabble Club pages - links to many more resources, plus information about monthly club tournaments in Cambridge, MA., which are especially welcoming to newcomers.
The Scrabble FAQ, maintained by Steve Alexander
Another excellent personal Scrabble page, by John Chew
The Official web site of the National Scrabble Association (NSA)
A great article by Steve Pellinen about how to become an expert.
Scrabble-related mailing lists:
Studying - jumbletime is a great, fun way to drill yourself on a wide variety of anagrammed wordlists. Create a free account, and study alone, or pit yourself against up to 5 others in a "room." Supports a small chat window, and players there are friendly and generally serious about learning.
Playing online via ISC - visit isc.ro, to create a free account and download Wordbiz, the java-based client. Once you're active there, consider making a support contribution - this entitles you to added features. Many legitimate tournament players from around the world compete there, and the site supports TWL, SOWPODS, French, Romanian (?), and "Multi". Some players even turn off ratings and the double-challenge rule, and play Clabbers.
Playing Scrabble online via telnet (text-based interface) - see John Chew's site
Useful books and products
My pictures from Waltham 2000
The rest of the
Waltham 2000 report, by Sherrie St. John