I want to apologize if I've made some language mistake.
First you'll need:
-Card Set with some good looking Ace of Spades or Joker (or some other card you like;)
-Pendrive or Mp3 player "guts" (I choose this second option)
-Very sharp knife
-A lot of glue
-Pencil or pen
-The last thing I've used were small metal plates which secure cards from holder.
Step 1: Preparing
-front with your favourite card
-middle where you'll cut hole for our memory unit
-and back group
Front and back groups should have the same thickness.
Then you should draw the shape of our memory unit on one card.
Step 2: Cutting
Be very carefull because it's very easy to cut to much.
After you've deal with first card you can use it as a template.
I've used holder to keep two cards together.
Step 3: Using Glue
The lowest card should be a whole card because it'll help you to assemble memory in right place.
When you glue every card you can use holder to impress excess glue.
Toilet paper will work as a sponge.
Step 4: Closing Memory Inside Deck
Wash your hands before you glue the last two cards!
Step 5: Ending
Also you can change the name of your new pendrive.
The last thing I want to tell you is, that this looks easier than it was in reality. Remember that!