Did you know you can add pre-built iCalendars to your Backpack Calendar? These make it easy to view US holidays, Red Sox games, movie openings, and more inline with your other events.
You can find a list of calendar options at iCalShare. Apple.com also has a list of iCalendars.
To add an iCal to your Backpack Calendar, copy the link of the iCal you want by right-clicking it (example: webcal://ical.mac.com/ical/US32Holidays.ics). Then go to your Backpack Calendar and click the "Add a calendar" link at the bottom of the right sidebar. Then paste the URL of the iCalendar into the field below "Name the new calendar."
If you want, select a specific color for these events. Then click the "Add calendar" button. The calendar's name will be listed in the right sidebar and the appropriate events will show up inline in the calendar. Click the calendar name again if you ever want to edit or delete it.
Where to begin? Major US holidays is a good start for Americans. Or try Moon phases (highly recommended for werewolves!)