I just experienced the need for an autosave in Blender (yes I didn't save after almost 2 plenty hours of work, too dumb I am...).
And thanks to the team behind it, there is already one !
When looking in my ~/.blender directory, I find several .blend files, with names like 34521 or 6318. I assume these numbers are PID for the several Blender processes which have runned on my station. These are usual .blend files, which can be opened with Blender. Looking as the most recent one, I found almost last state of my work (well, about 5 minutes before the X server crashed making me kill it from another host)
This is default behaviour for Blender, so make sure to check in ~/.blender (for Linux hosts, I don't know for other OSes) when you need it.