The Google Doodle for Father’s Day showcases a vanilla background, blue letters, and an orange polka-dotted tie (to substitute for the “l” in “Google”) to honor fathers around the world.

On the surface, it just looks like another Doodle to celebrate another holiday. 

What’s surprising, however, is the hawking of Google Voice.  At the bottom of Google’s home page, it reads: “Dad. Father. Pops. No matter what you call him, call your dad from Gmail.”

The link then leads to a page that lets you sign up to talk to “Dad.”

Google Voice calls phones in the US and Canada for free. International calls are cheap too; calls to Argentina cost $0.02 per minute and calls to Cuba cost $0.98.  A comprehensive list of international rates is here. 

PC-to-PC voice and video calls are also free.

Google Voice’s free services will stay free until at least the end of 2011.

Perhaps it’s a bit harsh to accuse Google of “hawking” Google Voice, a free and useful service that’s somewhat pertinent to Father’s Day.

Still, for all of Google’s “coolness” (Les Paul Doodle, anyone?), one should never forget that it’s a business trying to make money.  Or capture users, in Google Voice’s case.

The Father’s Day Google Doodle isn’t the only time Google has hawked its ware.  In Gmail, a message occasionally pops up informing users that Gmail works better with the Google Chrome browser.

Google’s grand strategy, judging from its cross-selling efforts and other actions, seems to be grabbing market share across a broad range of products and inducing existing Google users of one Google product to adopt more Google products.