Password managers help you manage your logins. They can store all your user names and passwords, along with login information and other notes. You only need to remember the single master password, instead of the many logins that you use.
If a manager uses a securely encrypted file, the file can sometimes be shared and updated among several systems. A single “master password” is used to protect the file. Many tools also will generate complex passwords, based on rules.

Multi-platform tools, and other options

• http://passwordsafe.sourceforge.net/relatedprojects.shtml
  • http://app77.com/pwSafe/
    • https://itunes.apple.com/us/app/pwsafe-password-safe/id520993579
• https://github.com/zdia/gorilla/wiki
• https://agilebits.com/onepassword
• https://keepersecurity.com/

Mac-specific info

Ebook, "Take Control of Passwords in Mac OS X, Second Edition"

• http://www.takecontrolbooks.com/passwords-macosx

Windows-only tool

• http://passwordsafe.sourceforge.net