Joann has a fantastic reusable cup for frappes (or milkshakes). It's sturdy clear plastic so you can see what's going on in it, it has a screw on lid so you don't spill, it has a silicone grip band so you don't drop it and it also prevents your hand from freezing while you hold the cup, and it has a hard plastic straw that won't collapse and has a bit of a propeller type thing on the bottom so that you can re-mix your drink should you need to. They also come in different colors so you can get one for every member of your family for milkshake night.
Starbucks also has a good reusable frappe cup. It is called the "Via" is is actually intended to be used with their new instant coffee. You will notice that it is also a sturdy clear plastic with a silicone grip. It has a screw on "sipper" top with a tab you can close to prevent spills rather than a straw but you can easily add a straw if you get a long one like the ones from Sonic or McDonald's big cups. You will notice that it also has a propeller type thing on the bottom, but unlike the Joann Cup it is mounted on a twisted stick (think drill bit). This stick has a tab on the top and when you move the tab up and down, the propeller spins thus mixing your drink. This mixing apparatus is far more thorough than the paddle on the straw, but the straw thing works fine for the minimal amount of stirring you might need to do. *Note* Do not use the mixer while your straw is in the cup as it might maim said straw. You know that comes from personal experience.
So there you have it friends, the culmination of my frappe studies. I hope that you enjoy making your own frappes in this simple on hand manner. Feel free to tweak the recipe to your liking, and don't hesitate to use flavored coffees or perhaps even flavored creamers to create your perfect summer frappe. -Kellie-