This little projects demonstrates the uDrive that can be set up as an extra drive on a PC. Copy files to and from the SD card, then put it in the uDrive and talk to it with 5 simple commands:
Read - Read a file off the drive
Write - Write a file to the drive
Dir - get the directory listing of files on the drive
Erase - erase a file
Initialise - send 1 byte at your preferred baud rate
Step 1: Connecting to your microcontroller
The uDrive works from 3 to 5V so can interface to a wide range of controllers.