Diversity is a mind-set. It's a way of thinking about differences and working with differences that transcend the obvious physical factors of race, gender and age. It can even transcend the sometimes less-visible but equally powerful dynamics of disability and sexual orientation.
For example, you may have policies for working mothers that rival that of Fortune 500 companies--generous maternity leave, flex time to accommodate parenting schedules, breast-feeding rooms, etc. But how do you handle the female employee who wants time off for her sick cat, or the gay male employee who wants the same amount of time off as an employee who has given birth? What if the employee is a never-married woman who needs leave for her fifth child?