A couple of years ago I took a course in Marine Ecology, for our final exam we have to do a lot of calculations using the Shannon-Weiner index (http://en.wikipedia.org/wiki/Shannon_index)

I wrote a program in my HP 48 calculator to solve it putting all the variables in a list, it's my favorite hack because I was the only one in the class who knew programming, so I finished the 2 hour exam in 30 minutes =)