ran into the same problem myself. i have stanza on the iPad, and you can add outside sources to obtain books, some of which you can't get any other way. either way, if you are using an ios device, this is what you do.
first go into stanza settings on your device, look for the control button i think (far right option in settings) and turn on the "export to itunes" option
plug the device in, wait for sync to complete in itunes, then click on the "apps" tab up top when you are viewing your device
at the bottom of the apps pane, there is a list of apps that allow for transfer through itunes, select stanza
select the books you want to export, click "save to" and set the destination... there you go