Free online screenwriting and scheduling tool releases v1.0
Celtx is a free open-source Canadian scriptwriting programme that connects with an online community where you can develop the script with other collaborators and writers. Unlike some of the other pretty cool free online scriptwriting tools, like Zhura.com, Scripped, PlotBot and ScriptBuddy - Celtx is a standalone piece of software so you don't need to be online to use it. It has built in storyboarding, collaboration, casting and scheduling features - all of which can be shared online if you wish to build interest in your film, and boasts 250,000 active users.
It also has a rather neat feature whereby scenes you assign to a date in your shooting schedule will import all information about all associated characters, props and locations into the calendar and automatically produce a call sheet.
You can download a copyfor Mac, PC or Linux.