There is one right here:
http://portableapps.com/node/20518
But you will have to update manually using Kovid's installer (drop it in the CalibrePortable folder, and it will begin the update next time you start calibre.)
IIRC Kovid expressed his explicit disinterest in dealing with the PortableApps system.
But you can drop any executable/program folder into the E:\PortableApps\ folder, and the menu will find it. You can then change it's sort type. It just won't have the flyover description.
Behind the scenes, they use different methods of allowing portability, but they both work just fine.
Now, if the updater feature worked, that would give me reason to care.
