Most memory card readers use specially designed ICs that handle all these in hardware logic. You can always use a PIC and implement the protocols in software. In that case, there is nothing much to include on the schematics other than the pic itself, and try to use a low-voltage version as most flash don't work with 5v. CF is mostly parallel, MMC/SD can be controlled via SPI. As I said, majority of the work is in software. And by using a PIC, don't expect fantastic transfer rates.