FYI Sparkfun has some SD card controller chips on breakout boards that you could use.

This is a Fat16/32 SD card interface that uses a serial UART or SPI interface:
http://www.sparkfun.com/commerce/pro...oducts_id=7955

This one is for Micro-SD cards but is not yet FAT functional, serial interface only:
http://www.sparkfun.com/commerce/pro...oducts_id=8567