Some of the tools that we are going to discuss today not only help with password generation but also act as simple and easy to use password managers. All you need to do is remember single master password or pass phrase. These tools help you generate strong password on the fly so that you do not actually have to remember passwords for your individual accounts.
Password Generator is a simple online tool that works in the exact same manner. Enter your master password and site name and it will generate the same 8 character password for you. They also have a bookmarklet version which picks up the domain / site name once you use it on the site you want to login to and populates generated password for you automatically in the password field. There is another tool called SuperGenPass based on similar idea. Unlike Password Generator, it allows you to build a custom bookmark by choosing your browser, the level of security for your master password and length (default is 10) of password to be generated. The problem with these bookmarklets is that if you have more than one account with different passwords for a given site (e.g., multiple Gmail accounts), it will not be able to make a distinction between two accounts and always generate the same password for both which may not be desirable.
A simple yet powerful tool that solves above problem is Secure Passwords from Digital Inspiration. Along with master password (pass-phrase), length and domain name, it also takes a user name as input to generate a strong, unique password for a given account. This automatically solves multiple account problem mentioned above. The source code is available on Github. You may download and host it on your machine if you are skeptical about generating your password online. The password is generated in your browser itself and no data is transmitted.
Lastly, if you are looking for something overwhelmingly comprehensive, do check out PasswordMaker as well.