Some months ago, I bought a 4DSystem’s µDRIVE-uSD-G1 (microDRIVE) from Sparkfun. It’s basically a serial module which let you access a microSD memory card (from 512Mb to 2Gig). You may wonder why use an external module as SD cards have a SPI interface? The main reason is … laziness. All file-system operations are performed by the module. So why bother coding fat16 support or whatever? Unfortunately, the current microDRIVE firmware only supports raw access.
Anyway, I wrote a small module for the current firmware. It was implemented as a template in order to support various serial implementations. The serial class must provide the following methods :
- uint8_t read()
- void print(uint8_t)
- int available()
It’d have been better if all the serial implementations derived from a same interface. But as I didn’t want to modify the base Arduino code (and as i said earlier, because I’m lazy), I went for the easy/brutal way. And you’d probably never have more than one microDRIVE. At least you want raid 
I tested Arduino‘s HardwareSerial and SoftwareSerial, as long as ladyada’s AFSoftSerial. None of the software implementations work 
Only soft read is working (hardware tx was used). As software serial is working for the serial LCD, I think the problem might be the autobaud detection during microDRIVE initialization… Or not…
Be careful! There’s a bug in the rev1 firmware. The internal memory address is not incremented to the next sector block after a write operation. It was corrected in the rev2.