System Preferences->International->Input Menu->tick 'Character palette' and 'Show input menu in menu bar'. Then go to the input menu, select Show Character Palette. It will now appear in all applications, however it will only work properly in applications that support Unicode (AppleWorks doesn't). In applications that don't, when you insert a character a different character appears in the application.
There are a few 3rd party applications you can use that will allow you to do the same thing (and will work in non-unicode applications), and will stay there in every application-Cocoa, carbon or classic. Two are PopChar and CharView (there may be others). These two are both shareware, and some characters are disabled in their unregistered forms.