Someone mentioned the tropical flavors of the Mexican-marketed Crystal Light, AKA Clight. I immediately hustled over to ebay and bought a big batch. So far, my favorites are the strawberry, mandarin, pineapple-orange and the soursop (guanabana). Each packet makes 1.5 liters of calorie-free goodness.
I have a few packets of flavors that are good, but not to my taste, that I am willing to send to people who think they'd like them. Just send me a PM with your mailing address and I'll pop em over to you.
FLAVORS: horchata canela (cinnamon horchata)
pina colada (pineapple-coconut)