Spark has a blog on 150 calorie or less cocktails...
An easy one I like (that tastes surprisingly good) is coconut rum with Diet Coke (or even better, Coke Zero).
Coconut rum is between 50 and 60 calories an ounce (depending on the brand), and has a nice flavor. Mixing it with anything reasonably low calorie (or no calorie) makes for a guilt-free treat! The diet coke and rum was my go-to drink on my beach vacation. Didn't want to drink all my calories!
Starting Weight: 260 lbs. (November 2010)
Quasi-Maintenance: 165 lbs. (June 2011)
Goal Weight: 150 lbs. (reached December 8, 2011)
Size 22W to Size 4
Currently maintaining within 5 lbs. (+ or -) of goal. I weigh daily, but also use a tape measure and the fit of my clothes to guage how well I'm doing.