FEZ Mini supports SD cards but there is no SD card connector on the board. For that, we will be offering an extension board with Micro SD connector. If you have some experience with electronics, you can always get any SD card connector and solder wires directly to the SD header on FEZ Mini. This new Micro SD expansion will be available late February.
Are the Eagle files available for the expansion?
On this thread I posted a schematic for interfacing a standard SD card to the Panda. http://www.tinyclr.com/forum/2/1200/. Just scroll down to it.
I have even butchered up a microSD adapter by soldering wires to the pads then shoving them in a breadboard - the diagrams below help to know what ones go where 
Thanks, even better.