From time to time, we all need to create a password. As a consequence of being human, we have a habit of picking really crappy passwords. Here are a couple of ways to generate passwords that should be more secure.
You can use pwgen in Windows, OS X (install through Homebrew or MacPorts, or Linux. It is also available online, although the online versions may not give you all the features of the program.
By default, pwgen attempts to create memorizable passwords that are somewhat random. Examples include In9taeme, Xo4eenet, and Riequig2. While not totally random, they are more secure than most methods of creating passwords. Using the program allows you to specify other requirements for the password and a more secure random mode.
Keychain Assistant (OS X)
Built into OS X, the Keychain Assistant handles secure password storage for the operating system. It also has a function to generate passwords. You can launch it from the application menu.
KeepassX (Windows, OS X, Linux)
I use KeePassX to store my passwords securely. There are other password wallets that you could use that would also generate passwords, such as 1Password and LastPass. I needed something that was cross platform though. It also has a feature to generate passwords.