With my N810 I run the GPE PIM series and Notecase on tablet as well as my Ubuntu desktop and laptop. These are DB file compatible and I can use the USB cable or Bluetooth to transfer files. I'm a Gmail user so I set it for IMAP and use the N810's modest mail package. I use erminig on the tablet to sync my calendar with Google. I don't know if these aps are also available on the N900 but they work well for me. With the N810, file sharing with Ubuntu is recognized by the tablet but it dosen't show any files in the File Manager. If the N900 has NFS then you could mount the tablet on Ubuntu and have access over a WiFi net with your PC.