Hi;
Two techniques are: hashing and encryption. Without knowing requirements, my first inclination is usually hashing. Because of the nature of hashing, you may need to take a closer look at the recovery procedures.
Check out my tools for data protection at www.visecurity.com/cryptg.shtml
Also, check alternatives to passwords: www.biometricsview.com
Regards;
Enrique Vargas
www.visecurity.com
www.vartortech.com