Want to manage finances within a group of people? Then EagleShare is the thing for you. Register for an account for free, ask your friends also to do the same. Then create a group for yourself. Add your friends and then you're set. Add activities. Activities are records of who spent how much money for whom on what. Once this is done, you can create reports instantly. EagleShare generates month-wise reports.
This EagleShare website was designed out of a serious need for such easy calculation of finances. Check it out here: Link