Actually, being a Samsung part it is located in the same package as the 256MB of SDRAM, which is soldered on top of the processor. Theoretically you COULD replace it, but it would require access to some rather expensive hardware, and it is rather hard to buy such chips individually.

Also, wongdg, you may need to check your numbers as they typically sell flash memory in MegaBITS and not MegaBYTES, so divide by 8 to get the maximum capacity; Samsung's 8Gb (1GByte) didn't exit sampling and enter production until well after the N900's design cycle ended.

The chip in the N900 is a 2GigaBIT device, the one in the DROID and N1 are 4GigaBIT (512MByte,) and nothing I know of uses the 8GigaBIT (1GByte) chips.