Calculate your caffeine intake
Ever wonder how much caffeine you're taking in each day? Energy Fiend provides a handy calculator to figure that out, complete with a checklist of lots of drinks and their caffeine content. My own consumption varies a lot depending on whether or not I'm working as a barista, but an average estimate puts me at 326 mg. That's two 8 oz. coffees, an espresso, and a Coke per day, putting me somewhat on the high end. On days when I'm getting up for work at 5:15 and taste testing the spro and coffee all day, I'm sure the number is higher.
The site also has a calculator to tell you how much chocolate or other candy you'd have to eat to risk death, given your body weight. 2900.63 Reese's Peanut Butter Cups would do the trick for me. Fortunately I can only eat 2900 before I get too full to consume that extra .63 of a cup, so I think I'm safe.
Caffeine's not as unhealthy as people tend to assume it is. In fact, it appears to have a whole lot of benefits. A certain libertarian coffee lover summarized them here.