I'm looking for something within Gmail that is similar to that within Yahoo mail. At the bottom of your mail screen, is your upcoming calendar events. I know about the Calendar widget, but it doesn't seem to work very well.
Are you referring to the Google Labs "Google Calendar Gadget?" If not, give that one a try. Note that it has a little "options" menu that you can use to enable/disable some features. For instance you can just show upcoming events or a monthly calendar or both.