Google Spreadsheets has a new feature that lets you solve linear programming problems. "Informally, linear programming determines the way to achieve the best outcome (such as maximum profit or lowest cost) in a given mathematical model and given some list of requirements represented as linear equations," explains Wikipedia.
Google's help center has an article that details how to use the new feature. You can test it using a template offered by Google, but it's not very intuitive and it didn't work for me. I got an error message when clicking on Tools / Solve: "The goal specified must be a cell containing a valid formula."