This software is absolutely amazing!
Since I use Windows, I use Gladinet Cloud Desktop. This gives me drive letter access to things like Box.net (wish they would have their own client), FTP, the list is awesome!
I have calibre via the "Connect to folder", post the ebooks it manages to Box.Net. Now I can access them using the Box.net software on my Playbook to read these!
And now calibre remembers the folder!