Hi!
As the topic says, how about a SD-MMC card adapter with
level converter on it for 3,3V to 5V signals and vice-versa.
Would make it very easy to interface with the SD-MMC
card to 5V systems!
Gravitech has one like this; http://store.gravitech.us/sdcaad.html
but I don’t want to order to Sweden just for one pice of
board. If Sparkfun had it I could bye it while I’m buying
other stuff here 
Sincerely,
Jonas Andersson
Sweden