the Internet Movie Database (IMDb)

[ http://www.imdb.com ]
still the best online database for information about your film. The clunky interface to add or correct data requires patience and some trial-and-error to get used to, but it eventually does work...most of the time (versus a few years ago when most submissions and changes to the data appeared to vanish without a trace).
Note that updates typically take 2-3 weeks before they appear in the database and do check back to make sure they appear and are correct. Also be warned that when correcting errors, misattributions, misspelled names appearing in credits, etc., that the performer, crewperson, or other entity that should be listed must have a valid entry of its own in the database before the correction will be accepted.

CineMedia

[ www.cinemedia.org ]
The Internet's largest film and media directory, with extensive, searchable lists of sites and resources dedicated to film, TV, radio, production, research, directors, organizations, schools, magazines, festivals, theaters, studios, and more. Biggest drawback may be a lack of subcategories and/or supplemental information beyond the links themselves, but an excellent resource nonetheless for the film and video professional.

"all movie guide"

[ http://www.allmovie.com ]
Mentioned here only because they are so widely used as a reference by other sites, the "all movie guide" gets two thumbs down: the first, for maintaining a database that's incomplete, outdated and full of errors and ommissions; and the second, for being totally unresponsive to repeated corrections, additions, and updates from filmmakers and talent.

Entertainment Law Resources for Film, TV, and Multimedia Producers

[ http://www.marklitwak.com/ ]
Mark Litwak's excellent and comprehensive site on entertainment law, financing, and negotiating deals and contracts. A must-visit site for any entertainment-industry professional.

NetSword: Stage Combat 101

[ http://www.netsword.com/stagecombat.html ]
Armed and unarmed combat for film and stage is less like doing it for real than you'd think. Here's a basic document on swordfighting for the stage, suitable for the beginning stunt performer.

MP3.Com

[ http://www.mp3.com ]
huge searchable collection of independent music, "radio stations," and information about mp3s
the "short form" URLs (e.g., mp3.com/bandname ) are not very reliable, but the pages themselves and the servers that stream MP3s from their site are very good

Internet Underground Music Archive

[ http://www.iuma.com ]
Discover unsigned artists, independent bands, local talent

The Writer's Pocket Tax Guide

[ http://foolscap-quill.com/wptg2002.html ]

Amazon.Com

[ http://www.amazon.com ]

Webshots

[ http://www.webshots.com ]
2.5 million high-resolution photos online in searchable, thumbnailed form
affiliated with excite and blue mountain arts, they do not pay for submissions unless you are specifically set up as a professional provider, but it can be an effective place to showcase some of your work and provide information on services and a link to your main site.