These are the calculators that I use and find to be the best for each financial area:

Auto Calculator: Edmunds has the best auto calculator that I have found. It takes into account taxes, registration and down payment.

Home Loan Calculator: There are plenty of worthy home mortgage calculators on the web. Realtor.com is one of the top realty websites and their home mortgage calculator the tops too.

Savings Calculator: This savings calculator takes into account into taxes, time and inflation.

Budget Calculator: One of the best budget calculators I have found. It has a place for take home pay and will give you a nice pie chart with how much you should spend a month.