Alan Chionglo Brief overview on how to write a play, the characters, making a story more dramatic etc.
Charles Deemer Advice on how to write stage directions when playwriting.
Coffee House Drama Workshop Nifty little website about the nuts and bolts of dramatic writing, including dramatic structures, script formats for plays, screenplays and radio dramas, screenwriting tips etc.
Northern State University Excellent FAQ about the playwright, necessary ingredients of a successful script, Aristotle's six elements etc.
Northern State University Useful FAQ on the process of playwriting.
Ohio University School of Theatre Course details for the industry recognised three year intensive Master of Fine Arts in Playwriting at Ohio University.
Playwriting 101 Very useful resource for anyone interested in writing a play. Discusses play structure, essential components, formatting etc.
Scriptware Playwriting software.
State University of New York Geneseo Excellent multi-part lecture notes by Melanie Blood on the tools and processes of a playwright. Includes discussion on the historical conventions of playwriting and a number of theatrical genres.
The Playwriting Seminars Excellent resource by Richard Toscan detailing advice and explanations on all aspects of playwriting, including structure, content, format, editing and more.