Best free screenwriting software

Look what I found! If you're into screenwriting or any other form of creative writing I have good news for you: This program is all that you could wish for and more. And it's for free!

Great features of the program CeltX:
- Character sheets
- Script formatting
- Note functions
- Online sharing/colaboration
- Project calendar/schedule
- Image/video/sound support on character sheets/background
- Integrated browser for research
- Open source and broad support: Win, Mac, Unix...