Silentum PasswordGen is a handy password generator tool if you need passwords for email clients, message boards, IM programs, or any other protected pages. It has various options, including choosing whether to use lowercase/uppercase letters, numbers, symbols, and spaces, in any combination you desire.
Its character limits extend between 5 and 50, and you can generate 1 to 5 passwords at a time. You can use this for your own personal use, or place it on your site to allow visitors to generate their own passwords. It runs entirely on a single PHP file, and doesn't require any MySQL.