I managed to get a shell over USB to my PRS600. So I'm attaching a video (sorry about the quality, but it should show the idea) and everything required to get a shell over USB going.
In usb_con_2010_05_06.tar.gz there are two things mainly:
- test - porkupan/igorsk loader with a small mod from me
- reader - to put on the SD card
I wrote detailed documentation (README in each dir) on how to install and use both of these (not just to get a serial console, but in general) as well as an explanation of how everything works, what you need to get to make your own programs and how to compile the kernel modules yourself should you want to. Oh, and also some warnings about what can go wrong and how to prevent it.
Since I don't use windows, the instructions are a bit linux-centric. Since the PRS600 runs linux, I'm guessing people who want a remote shell on it have access to a linux or similar machine anyway.
I also included the program that draws the silly pattern (Sierpinsky carpet) in the video, because it's got comments on how to manipulate the screen (although I made a post about how I figured that out before).
Now that I have a shell, I can kill tinyhttp, open /dev/ttymxc1 myself and see if I can figure out how buttons and the touchscreen work. This might take a while though, so I'm taking this opportunity to release what I have.
If this sort of thing interests you, I hope you find it entertaining :)