I had a look at WriteRoom a few months ago and wasn’t impressed, but Leonard just convinced me to give it another look and I’m completely sold. It’s a free text editor for OS X with two killer features:
A full screen mode (toggle with ESC) that hides the rest of your screen, letting you type in glorious green-on-black courier with absolutely no distractions.
Autosave. You never have to save a document, even when you quit WriteRoom. It maintains a list of your WriteRooms in the file menu, keying each on the first few words. If you want to move text to an actual file you need to either export it or use copy and paste.
I’ve lost count of the number of times I’ve lost some notes to a crash having scrawled them in TextMate or SubEthaEdit without saving to a file. Auto-save / auto-recovery should be built in to every application.