We have all of these calculators on vancity.com, and one of them helps our site visitors decide if they are better off renting or owning their home. It turns out that The NYTimes does it better. They have a nice little flash tool to determine whether owning or renting is a better way to go given rent increases, market value shifts, downpayment percentages, mortgage rates, etc…
PS: Thanks for the link, Ruben.