As anyone who uses Gmail and other Google web services knows, Google has already implemented a global contact list. When you want to share your Google Calendar with a friend, the site already has all of your Gmail contacts stored for easy retrieval from a drop-down list. The same thing happens when you want to share an RSS item from Google Reader or a spreadsheet from Google Documents.

So why on Google Earth doesn’t the company offer Google Address Book? Think about it–a globally-accessible list of everyone you know, searchable by name, hometown, company, email address, or even zodiac sign. You could browse a gallery of images associated with your contacts, or automatically add their blogs’ RSS feeds to Google Reader to keep track of what they’re up to.

Every person you email with Gmail already gets automatically added to your contact list. It’s just a small step to add an option to send someone your digital business card, which can include any contact information you choose to share (this functionality has been built into Outlook for years and years), so that your correspondents can easily save your info to their own address books. And of course you’d be able to import your current address book from Thunderbird, Outlook, Outlook Express, Palm, etc., as well as manually inputting new or changed contacts as they come along.

What’s the best part about this? Half the work is already done! Google already integrates your contact list into all these other services, and although it’s not incredibly easy you can already add email and mailing addresses, phone numbers, and other information for each of these contacts. All Google would have to do is put together a simple Googley site (the aforementioned Google Address Book) to make storing, browsing, and searching your contacts easy (and rewrite some code for the various services to take advantage of the new functionality).

A couple of other useful features, off the top of my head:

• Tags
  Tags can replace email groups. Tag all of your business contacts “business.” Tag all of your drinking buddies “booze.” Tag your roommates “roommate.” Tag your family “family.” College friends, “college,” high school friends, “high school,” and so on. And if someone fits in more than one category, no problem–you’re not limited to one tag per contact. From now on, when you want to invite everyone over to watch the Super Bowl you can just click on “send to tag” and select “booze,” “college,” and “high school” and send your mass email to everyone with those tags.
• Birthday integration with Google Calendar
  This one’s a real no brainer. You go to your Google Calendar settings and click on the “Birthdays” tab. There you’ll see a list of every contact for whom you have a birthday listed. You check the box next to anyone whose birthday you want to appear on your calendar, and choose whether you want a default reminder a few days or weeks in advance (and of course you can change this setting manually for each contact).

And I have no doubt that anyone dedicating more than 30 minutes to this idea could come up with many more.

I’ve got to believe that Google is already working on this. It’s not a complicated idea. But on the other hand I would have said the same thing a year ago, and I haven’t heard or read anything to suggest that they’re about to release anything along these lines. So on the off chance that this hasn’t occurred to anyone out there in Googleland, consider this my gift to you. Just do me a favor and let me in the private beta when you get it up and running.