Given that we often have a need to generate secure passwords for the likes of web applications, blogs, social sites, etc. I've been using a wee utility called PWGen for Windows.
PWGen is a password generator capable of creating large amounts of cryptographically-secure passwords or passphrases (from word lists).
It's small, doesn't write to the registry or hard disk and you can choose to use either the number of characters and a character set or use a number of words passphrase.
For Mac OS X, you could use the similarly small and unintrusive RPG or Doorman utilities. Both are free and available from the App Store.
Alternatively, there are some useful online password generators...
- PC Tools Secure Password Generator
- Strong Password Generator
- EverPassword Password Generator
- Free Password Generator
- Secure Password Generator
- Ablazesoft Free Online Password Generator
- Techzoom Password Generator
- Password Crackers Free Password Generator
- PassPlex
Also, once you've got your secure password, it's worth checking it with Microsoft's Password Checker.
