I’m always curious about tools that other writers use, so here’s my contribution to the discussion.
MacBook Pro. I switched when writing my non-fiction book, after a particularly nasty system crash that corrupted a bunch of saved data. TextWrangler. Everthing gets written in to txt files, possibly as fine-grained as one-per chapter. I use a simple structured text format, with *bold* and ~italic~. When I need to send something out according to specific formatting guidelines, I have some old python scripts that convert things for me.
Every few days, I check in the entire directory into Subversion. This is not only supremely useful in allowing me go “go back in time” to earlier versions, but the checkin logs also tell an interesting story over time. And yes, this is a form of off-site backup.
For outlining, I use either plain text (note developing theme here) or Tinderbox for times when I need something more visual. I print out the outline in a teensy-tiny font with multiple-columns to that it fits on an a single page which gets several layers of notes scribbled on it. I keep lots of stuff in Evernote too, especially if I might need to access it from my phone at some remote coffee shop.