I already know of the Environment.getExternalStorageDirectory method (it returns the string /mnt/sdcard). In the case of Samsung devices. The data goes in to the external memory but not the removable SD card. The path to that is /mnt/sdcard +/external_sd.
So does the extra subfolder vary from manufacturer to manufacturer? Is there any way we can find out the path of a removable memory device?
Not generally. Those are outside the bounds of the Android SDK at this time. The Android SDK only supports standard external storage, not anything else.