About a year ago I wrote the original article which this one is based on, but I recently decided it was and important subject and it needed to be expanded with more information.
The problems is that most of us are swimming in passwords, and we have a hard time remembering all of them. To deal with the password overload, people will use different unsecured methods like writing them down store them in obvious places on a post-it note under a keyboards, a phone, a mouse pad, even under or in a desk drawer. Others write them on notes and leave them on their monitors or computers.
You could created encrypted document of some type (e.g. text, Word, Excel, etc.) to store them. There are also several password management applications available for you to download, some are free and others cost money.
Although before you pay for anything or try other programs. Check out a program called KeePass. This is a multiple platform, open-source password management application. There are also 3rd party ports of the application that work on popular mobile platforms (e.g. iPhone, Android, etc.).
KeyPass will store your private data in an encrypted file, so even if someone steals it they can't read it unless they know the master password. Check out the web site for more information.
Note: KeyPass needs its data file to be shared with a file-based sync solution such as Dropbox to be utilized among multiple devices (e.g. PCs, Macs, iDevices, and Android Devices).If you want something that offers more features then KeyPass, checkout some of the commercial password management solutions like: