Script Surgeon
Script Surgeon

Links

Unions

Writer's Guild of America, West
The place to go for union issues in the USA and to register your script
Writer's Guild of Great Britain
The place to go for union issues and a cup of tea

Blogs

John August
A ton of useful ideas from a pro - writer of "Go" and "Big Fish" among many others
Jane in Progress
Jane Espenson is a TV writer, currently working on the Battlestar Galactica spin-off "Caprica". She's retired her blog now but the archive is well worth checking out for her thoughts on what pilot scripts to write, what stale jokes to avoid and how to spice up your action lines.
Writing for Performance
Robin Kelly always has his ear to the ground. A great place to come for interviews with writers, and UK-based writing opportunities.
James Moran
James Moran's blog is always worth reading. Start with this astonishingly comprehensive "Big Writing FAQ".

Software

Final Draft
The industry standard and not expensive.
Movie Magic
The only serious rival to the above. Less well-known and more expensive, but its users say it's wonderful.

In general we recommend you stay away from software which offers to do the actual writing for you!

Other resources

How to lay out a screenplay
Software like Final Draft takes care of this for you and there are as many subtle variations on this basic template as there are screenwriters but this guide gives you the basics in a fairly clear way.
BBC Writers Room
Full of advice, templates, sample scripts, opportunities and ideas.
Wordplayer
Genius site run by Ted Elliot and Terry Rossio (Pirates of the Carribean / Aladdin) full of wit, insight and practical industry advice.

Screenwriting / Storytelling manuals we like

Impro by Keith Johnstone
The book that made Mark Ravenhill into a playwright (among many others).
The Improv Handbook
More thoughts on spontaneous storytelling, written by two of the script surgeons.
Story by Robert McKee
Solid advice, but doesn't pretend to be an infallible template (pace Charlie Kaufman)

Screenplays available to read online

Drew's Script-o-Rama
Hundreds of downloadable movie scripts.