I've made them for my family for Christmas 2009 and the really liked them (at least they pretended to ;-))
Check out this video:
UPDATE: Since 2011 you can buy the offical LEGO® Minifigure USB Flash Drive here. But considering the price and the looks of it, I still think it's a good idea to make them yourself.
Step 1: What You Need
a very small usb flash drive (e.g. EagleTec USB Nano Flash Drive or Delock USB Nano Memory stick)
(e.g. from http://usb.brando.com/eagletec-usb-nano-flash-drive_p00892c041d15.html or ebay)
- a female Lego figure wearing a skirt
- self-hardening synthetic clay (e.g. “Apoxie® Sculpt”)
- a 2 by 2 black lego plate
- a box cutter
- a Dremel (Felt Polishing Wheel, different grinding stones, precision drills)
- a small slotted screwdriver (to apply the clay)
- sandpaper (800, 1000)
- a black permanent marker
Step 2: Modify the Flash Drive
Then apply the clay to secure the parts (use as little as possible), as shown in the picture. Make sure not to get any inside off the metal part.
Step 3: Modify the Lego Figure
Then take the bottom part, drill a few holes into the top (remember to put something underneath it. I drilled into my desk...). Now use the grinding stones to mill away as much from the inside as possible. Use the sanding paper to grain away as much of the outside of the cap as possible.
You will have to repeat this, until the cap fits into the bottom part. It's not bad if you mess up a bit, as long as you don't drill into the front part and the rest of your bottom part is black.
Step 4: Apply the Apoxie Sculpt
Let the part dry over night and grain away the extra clay, with very fine sanding paper. Paint the clay with the permanent marker and use the Felt Polishing Wheel to smooth the colour.
To make sure, that the drive fits perfectle into the figure, put the flash drive into the bottom part and place the top part on top of it. If it closes use superglue to glue the drive into the top part.
Now use the Apoxie Sculpt to fill up the hole between the flash drive and the upper body, as shown in the third picture. Let the clay dry over night, paint it and smooth the colour.
Place your lego figure on top of the 2 by 2 black lego plate and...
HAVE FUN WITH YOUR NEW FLASH DRIVE!