Dan Frakes at Macworld shares some helpful hints about unlocking the secrets of the Keychain:

Passwords, serial numbers, ATM codes - we’re all swimming in a sea of information that’s secret (or should be). Make it easy to remember, and someone may swipe it. Make it hard to guess, and you may forget it yourself. Mac OS X has the answer: the Keychain. Here’s how to use the Keychain in OS X 10.3 to hide all sorts of information, from password hints for Web sites to notes on a confidential business deal.

Keychain Access
If you’ve ever entered a password in your Web browser or e-mail client, or provided a password for an encrypted disk image, your Mac has probably asked whether you’d like to save that password to your Keychain. In addition to accessing your keychain through these dialog boxes, you can work directly with your Key-chain via Keychain Access (Applications: Utilities).

OS X’s Keychain goes beyond password protection. You can store secure notes in it, too.
When you launch Keychain Access, you see a list of all the items in your Keychain, including information about each item’s name, kind, creation date, and modification date. If you haven’t opened Keychain Access before, most of these items will be passwords - Internet passwords, application passwords, disk image passwords.

Select any password item to bring up information about that item at the bottom of the window: the item name and kind; the account name (if applicable); and the specific URL, application name, or disk-image name for which you use the password. You can view the actual password by selecting the Show Password option and entering your Keychain password. To paste a password into another application, click on the Copy Password To Clipboard button. You can also add comments about the item - say, to remind you what a particular item is for, or to include a Web site’s password hint and answer.

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