E-magazines:
Creative Screenwriting Magazine site: http://www.creativescreenwriting.com/
Hollywood Scriptwriter Trade Paper site:http://www.hollywoodscriptwriter.com/
Hollywood Literary Sales site: http://www.hollywoodlitsales.com/
Screenwriters Utopia: http://www.screenwritersutopia.com
Organizations:
Writers Guild of America (West) site:http://wga.org/
Writers Guild of America (East) site: http://wgaeast.org/
Books, software, etc.:
The Screenwriters Store site: http://www.screenwriterstore.co.uk/
Vast collection of free, downloadable screenplays to popular films:
Drew's Script-o-Rama site: http://www.script-o-rama.com/