This was mentioned somewhere (I think it was Writers' Room): www.scripped.com
Allows you to work online and keep scripts online too. Only just tried it and it looks good for American TV format (maybe no use to anyone here!) and looks like it might be good for working from scratch, as I've tried to import but imports in .txt format, so you have to mess around a lot with it.
It is easy to use though. Also, it keeps your scripts online so someone else has to worry about the backups and all that. And an off-site backup is always good to have. (So, even if you just bung the unformatted text of your scripts
in there, you'll have a backup of sorts)
Anyway, it's free and it's backed up.
Dan