Dark Room / Write Room

For all your writing needs: http://they.misled.us/dark-room

Or for Mac: http://www.hogbaysoftware.com/product/writeroom

Basically old-school text editor emulators (but with more modern functions built-in).
I haven't had a chance to play around with them yet, so I don't know how well the auto-save feature works. Anyway it seems more useful for getting started on projects than for revising major papers --- but it's nice to have an uncluttered (digital) workspace sometimes.

Kudos to Prof. Parikh for the heads-up on this one.