MyTextFile is an online text editor that also supports full screen mode for distraction free writing. You can log into MyTextFile with your existing Google Account as it is built using the Google App Engine.
MyTextFile is extremely simple (you can have one file per account) but it does offer some useful options. For instance, you may change the foreground or background colors, turn on Auto Save (to recover work in case of browser crashes), change fonts, etc.
It also preserves an history of all your document change and you have the option to selectively delete any particular revision. Now Google Docs can do all this as well but MyTextFile may still be worth exploring as it is light, simple and allows download of text files.