Adafruit has a very nice Proto shield with a real time clock and a sd module on board. As you can see, this takes a regular size sd card, or a micro sd in a conversion carrier. At under $20, this is a cost effective replacement for discrete RTC and SD modules, and a proto shield. It does not come with extended headers, so it either has to be the top shield in a stack, or get a pack of extended headers and solder those on instead of the normal headers included (but not installed). We have several projects coming up using this shield, so stay tuned.