I accidentally discovered XNJB on VT, and installed it in the hope that it will be easier to transfer mp3 files from iTunes to the a737's 2GB micro-SD card than via Bluetooth (direct transfers, which work fine, require unplugging the micro-card plugging it into an adapter, etc. and Finder+Spotlight put a few extra hidden files on the card, which show up on the Music-Player of the phone).
XNJB does connect to the phone, but just like the Bluetooth transfer, automatically transfers the files to the Music folder on the phone (which has only about 25 MB free) rather than the SD-card.
So if you want to transfer a few longer Podcasts, you need to unplug the USB cable, move the files to the card, to make room on the internal memory, and then reconnect. XNJB , just like Bluetooth, does not allow you to choose the card as a target, though it sees it as a source for transfers from the phone to the Mac.
When XNJB finds that the internal memory is full, it just gives a cryptic error message, and sometimes even quits "unexpectedly." Though the transfers are faster than via Bluetooth File transfer, the latter is more stable.
Let's hope that the developers read this and will overcome these limitations in future versions!

BTW -- My Mac is an 24 in 2.16 GHz iMac with 2 GB of RAM OS X 10.5.4; the phone is a SGH-a737 from AT&T with a 2 GB micro-SD card, software version A737UCHD2