I stumbled across these instructions on how to make a homemade Starbucks frappucino the other day, and finally got around to experimenting with the recipe today.
Here's what you need:
Add to blender, and blend. Here's what you end up with:
The one thing I did wrong was use hot coffee - this reduced the ice particles to nothing. Make the coffee a day in advance and make sure it's cold. Still, the gelatine mostly prevented the drink from separating - if you let it sit long enough, you'll still get some separation.