Fun visualization site: Information is Beautiful
I think I would get along well with the creator of the site, David McCandless, who, on his About page, says, "My pet-hate is pie charts. Love pie. Hate pie-charts." It's not surprising that he has written for Wired before - his visualizations look to be very much in the Wired style of infographic. Here is one I saw featured on Lifehacker that could prove useful:
According to McCandless' scatter plot, the most bang for your buck in terms of high caffeine and low calories is iced coffee (lower-right of chart), while the worst is a hot chocolate with whipped cream (upper left of chart). I'll also point out that iced coffee, like regular coffee, is cheaper than espresso-based drinks, and most people are actually capable of making it at home, so it seems like an easy choice.