I had to sign up after i googled pretty much the same exact question just now and to see that you beat me to the punch by a day!
I was thinking along the same lines as the retro fitted microwave http://www.raspberrypi.org/archives/4358
that was shown a couple of weeks ago.
An older washing machine would have the main components required (the barebones and parts) the raspberry pi could be used to control and run each sequence.
I believe you could gain a lot of efficiency by creating your own programs, I would like to try this out at a time when it would be possible for me!
I can see lots of possibilites.