PS7 does, but CS and above don't. I just looked it up because one of the managers at work is a BIG computer geek like me and we were (surprise) talking about computers and how we do/don't let our kids use them...he told me to see if there was autosave because the version of PS he had did allow it. Anyway, I found out 7 did, but CS, CS2, and CS3 don't have the option.
I know, though, that you can set timers up on your computer to do things randomly for you, so I'm thinking of seeing if I can make it autosave for me. Otherwise, I lose WAY too much stuff...I should have learned by now, having lost 4789152894 things, but no...I still don't save regularly! LOL!