Yes dude the USB on the go cable available for nokia devices directly from nokia itself. click here to view that cable. click here for the compatible list. Unfortunately out nokia n900 is not in the list. But it look like the phone's listed in the compatible list & our n900 too has the same data cable socket. So it should work. Btw i ll confirm it once speaking with the nokia care line

This is for noobs:
With this cable you can connect your nokia devices directly to USB drives without the need of a computer to transfer files between them