I use the free version of Lastpass, an excellent online vault for all your passwords. You set 1 master password that logs you into your secure vault, and then you save all your passwords in the vault as you go.
It has a checker system that scans your passwords and tells you how strong they are. They help you to strengthen your passwords and also generate really strong passwords if you can't think of anything! All free too!
There is a pro version, but I don't use that. You can download it as a browser extension (I use it in Chrome, but also have it for Safari). Try it out and let me know what you think.