I get cravings for sweet things from time to time, and a lot of times typical commercial smoothie mixes (frozen section), can contain A LOT of extra sugars, fats, and other not-so-friendly items.
I like to take a plain bag of frozen fruit (I really like Sunrise Growers Cherry Berry Blend - under $3 I believe at Wal-Mart), and add it to 1% milk and two packets of Splenda. Blend it up in my smoothie cup (these are super cheap at Wal-Mart, as low as $16!), and relish in the deliciousness that is my concoction!
I had one last night, added all the calories and whatnot, came to 192cals, 5g fat, and 9g protein - and totally hit the sweet tooth that was becoming a nuisance.