How you incorporate mini-boards
In November 2011 there was an extended discussion at moc.spuorgoohay|sresu-dacik#moc.spuorgoohay|sresu-dacik under the subject line "Creating a Footprint".
I never did quite figure out what the original poster wanted, but the discussion gave rise to various things.
If you were wanting to design a PCB which, among other things, would have one of these plugged into it….
(That's a carrier and circuits for an SD card. At November '11, it cost $15 from http://www.gravitech.us/micaad.html)
Then one answer would be to design your own component to represent the miniboard, and a footprint to go with it. Here you see a schematic using one of the SC card miniboards. (The schematic is mostly non-sense, but it illustrates what I want to illustrate….
… and here's a PCB to implement the above. Again, it is not a "brilliant" or efficient PCB design, but it shows the special footprint in action.
(Throughout this page I've used "mini-board" where many people in everyday life… well may electronics hobbyists, anyway, might use the word "module". I've avoided using "module" for the mini-board, as KiCad uses the word module as a synonym for "footprint", and I didn't want the two meanings for the m-word to create a path to confusion.)