This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
I did some scientific programming years ago. The two ways I checked for equality were to compare the absolute value of the difference to a small number and (more accurately) to subtract 1.0 from the quotient and compare the absolute value to a small number.
For financial applications, double is for homework. Real applications use BigDecimal.