I’m one of those people who think that Google Calendar is the best invention after sliced bread and indoor plumbing (and Gmail, of course). I’ve been using GCal for a multitude of things, such as for SMS reminders, simple task and appointment lists, and such. One other great thing I can do with Google Calendar is add various other calendars to my current view.

While you can add anyone’s public-access calendar to collaborate via Google Calendar, you can also add a variety of public calendars to your view, so you can be notified of any upcoming event or important date. These include holidays, public events, movie schedules, campaign schedules, and even the moon phases, among others.

Adding public calendars to your view is easy. First step is to click on the Add tab and click Add a public calendar.

You will then be presented with a list of the top picks. You have a choice of categories, including TV shows, Events, Sports, Entertainment, Miscellaneous, Holidays and Google’s own public calendars.

TV Shows has show schedules and times for a select few channels like Discovery. Events shows schedules for local events, where applicable, like concerts and other recreation events (via eventful.com, mercurynews.com and other sources). Sports listings features various sports schedules like those for the NFL, NBA and also local sporting events. Entertainment includes Netflix DVD releases, video game releases, Atlantic Records tours, and other listings in the world of entertainment. The Miscellaneous listings, meanwhile, include the campaign calendars of various US Presidential hopefuls.

These listings are a bit limited for now, in terms of number but I think they’re promising. When applied to localities, Google’s public calendars can be a very powerful tool for tracking and setting up local events.

Perhaps more useful are the lists of public holidays–you can select and add from among 39 countries. Also useful are the Google development calendars. Personally, my top picks are the phases of the moon calendar and the AdSense calendar (so I won’t forget when the checks are en route).

Adding any calendar just requires a click on the Add to Calendar button.

When a public calendar is already added, it says so.

And you can view these already on your own GCal, with user-customizable colors, of course.

You can remove public calendars from your view by going to the Manage Calendars link under your calendar list

and then clicking on the trash can icon beside the title of that calendar you wish begone.

Or, when things get too cluttered, you can simply un-tick the checkbox beside that calendar on the calendar list.

Hopefully Google will add more choices of calendars, and will eventually add in location-based data. For now only US ZIP codes are accepted, but I’m optimistic Google will add more regions soon, given enough demand for data, and enough data-providers willing to share information.