This took a bit longer than I expected but I've finally gotten this project to the point where I feel comfortable I can go public with it. And reveal just what the heck has been sucking down all my time recently.
I've developed a mountable Sony Reader Filesystem.
What the heck is that you ask? Well rather than an application such as the wonderful libprs500 or the Connect application supplied by Sony this piece of code isn't an application.
You insert a SD card and the operating system uses some code to read the contents of that SD card and present the contents as files and folders. This piece of software does the same task, but for the Sony Reader.
You can then use your favorite tools to explore and modify the contents of your Sony Reader. On the Mac you can use Finder or Terminal. If you are writing an application to bind ebooks or RSS feeds onto the Sony you can write the data to the Sony Reader as if it were a regular collection of files and folders on the computer itself. For example, you can have Word 2004 export an RTF file directly to the Sony Reader.
The code is written using FUSE and libusb. This allows the same code base to work on Mac, Linux and FreeBSD. There is no Windows version, but heck: you've got Sony's CONNECT software on Windows right, you don't need this.
First release is for the Mac. You will need Mac Fuse from Google: http://code.google.com/p/macfuse/
and libusb: http://www.ellert.se/PKGS/libusb-0.1...usb.pkg.tar.gz
Code later today.