Thank you very much, eschwartz! As you have seen, thanks to your help in another thread, I have jailbroken and installed the firewall.
Pghaworth, thanks for the instructions on how to browse a Calibre library using the experimental browser. I was hoping for something that requires a little less action on the part of the user.
KindleButler seems like a good option, although it isn't quite automatic (and requires a working USBNetwork installation, which is difficult to get working).