Firefox + paper for more important ones.
Just a Tip on Firefox, make sure to setup a master password for Firefox (Tools / Options / Security). If no Master password is setup someone can easily access the security section and view all your passwords.
There is no option for documenting passwords with a office document (MS word, OpenOffice). That is what I do.
That's true, sure you're not the only one doing that but in the hopes of keeping it simple, just vote "Other".
Also just a tip if you're relying off a software notepad might as well use a password manager such as
KeePass. It's 100% free and will encrypt your data. This is a much better solution since anyone who has access to your computer could access that file and have access to all your passwords.
You may not think the above suggestions are issues if you don't have anyone else using your computer but if it were to be stolen, they'd immediately have access to all your login information.