The trick is to have ubuntu -> smb sync and smb -> Android sync. The payable apps sort it out in one go, but hell, we're not paying for this hack.
- set up the smb. I used old laptop drive hooked to BT Home Hub mark 1.5. Please note that the usb voltage is not enough so if you're not using USB sticks it's better to have a external 5v supply to the disk. The disk have to be FAT32 formatted. I've formatted mine and run it at the standard charger (it's 6v so will tell you when it will fry).
- set up ubuntu smb sync. It might require dumping gnome mount and going straight for fstab. My entry is //192.168.1.253/bt_7g /media/NetworkDisk cifs username=USERNAME,password=PASSWORD,file_mode=0777,dir_mode=0777,users 0 0
- once you have that you can set up sync, purists would prefer rsync, I used conduit - dead simple.
- Create relevant folders in the sd card
- The last step is to install samba client on the android. I've used PCFileSync Simly add folders on the sd card and the smb folders created in previous steps and sync.