Ya know, you could always put the blackberry in mass storage mode and just dump the files you want onto the SD card. As long as your version of linux supports things like thumbdrives, you should be able to do that with no problems.
You don't even need to dump to an SD. As long as your BB is in Mass Storage Mode, just plug it right into your computer, and it will recognize it as a drive, you can drag and drop files to and from your computer this way.
I run Ubuntu 9.04, and as soon as I plug in my BB via USB, two new drives pop up, one for the device itself, and one for the memory card installed in it.
Word of warning, in case you don't know...drives are not hot-swappable in Linux. Make sure you unmount them before disconnecting.
Edit: just realized Polychrome was talking about dumping to the SD card on the BB, not to a separate card. So, yeah, like he said.