The Dashboard is fun and all, but few widgets offer much in the way of storing any kind of data in a secure way. If you would like to work with a scratchpad in the comforts of Dashboard but also want the notes you jot down to be secured from wandering eyes, Secret NotePad might be a good option. With support for multiple pages, locking itself and even clearing the clipboard, this is perhaps one of the most secure widgets you'll find this side of the Mac OS X Keychain. Oh, speaking of the Keychain: all the notes you create in Secret NotePad, and even the original password you create to secure these notes, are stored in the Keychain for easy backup and synching with .Mac and similar services.
Upon opening Secure NotePad, you are presented with a small dialog asking you to create a new password just for locking down the notes you store in this widget. This dialog doesn't allow you to verify or even see the password you're typing though, so make sure you're getting it right. After that you get a simple resizable box into which you can paste plain text. Clicking the lock icon in the upper left of course locks the widget, scaling it down to nothing but the title bar and the password entry box. No password, no dice. Flipping the widget over presents options for locking the widget after a certain amount of Dashboard inactivity time, clearing the clipboard, default font/size and even locking the Keychain when you lock the widget. Truly, this is one widget your nosey coworkers won't get very far with.
Secret NotePad can be found in Apple's Widgets directory.