If you want to solve or create crossword puzzles, there are some resources you should know about.
The grand collection of everything crossword (that's “everything” with a lowercase “e”—not an Adams Media title) is Ray Hamel's http://www.primate.wisc.edu/people/hamel/cp.html. This should help you find anything out there related to crosswords.
If you're just looking to solve crosswords, I'd like to recommend the Newspaper Puzzles section of Dave Fisher's http://puzzles.about.com/cs/crosswords/; I think I started out here before miningco ended up under About.com (if you go up a level, you can also find cryptics, diagramless, and other variants).
If you're ready to compete, or just want to meet some of the top solvers and constructors in the country, there's the national tournament held in Stamford, Connecticut, run by Will Shortz; he edits the New York Times crosswords and runs “The Puzzler Presents” on NPR. The tournament's Web site is: www.crosswordtournament.com.
Like playing with words in general? Perhaps you should check out the National Puzzlers' League (NPL) at www.puzzlers.org. I'm not just a client, I'm the … wait a minute, I'm just a member.
Wondering what software there is out there for solving or constructing? Crossword Compiler seems to have become the standard, although you may also want to consider Across Lite (a solver), Crossdown, Across, and Crossword Maestro.
Perhaps you're looking for a forum; a place to learn the recommended rules of construction, ask questions, or even solicit special projects. A place to comment on new lingo and people that may be ready to start showing up in puzzles. A place to ask about how dubious a certain grid entry is. The place to go is http://www.cruciverb.com, which also has a asic Rules page and a Sage Advice page, which might easily answer your construction questions.
Maybe you're working on a puzzle (solving or creating) and realize that you need to look something up, like “I know there was a character named in a movie, TV show, or play I saw.” Well, for movie and TV, www.imdb.com is a must, and www.itdb.com is helpful for the theater. You probably want a good dictionary and thesaurus on hand, maybe an atlas, book of quotations, and reader's guide, too.
There used to be a group on the Net called rec.puzzles.crosswords. While old, its information is still useful: hppt://thinks.com/faq/crosswords.
There are a lot of good word list files out there for making crossword puzzles with; just make sure that you edit in the good, and edit out the bad from them. The NPL's www.puzzlers.org/secure/wordlists/dictinfo.php is a good place to start, and includes Grady Ward's Moby dictionary, the largest dictionary out there, methinks. Or, for some categorized lists, you might want to try www.phreak.org/html/wordlists.shtml (or www.cotse.com/tools/wordlists.htm if you'd rather not unzip the files).
And, of course, my personal plug for my own Web sites at www.geocities.com/xwdguy and www.themecrossword.com.