Assign a custom icon to your flash drive
Lifehacker has a tip on how to Assign a custom icon to your flash drive.
By putting a unique icon on each drive with an autorun file (instructions are given), you can get a unique symbol for each flash drive you use.
ADDITIONAL TIP: to add to this, you can use:
so that a listing shows both your icon and your name and phone (or whatever you prefer) to get it back to you.
If you make this file hidden and read-only, it will not be as easily changed.