Here's a great article from Elinor Mills over at C|Net News.com that tips us off on plans by Google to start including coupons on Google Maps:
Searching for bargains on Google Maps (C|Net News.com - Aug.14/06)
An excerpt: "Beginning Wednesday morning, Google Maps users will see coupons from the more than 12,000 advertisers who offer printable online coupons from direct-mailing provider Valpak." (Read the full story..)
Update: It seems some coupons are now viewable. Search for "Great Jones Spa" from Google Maps and a "Coupons" link appears below the search result in the left column. Clicking it brings you to the screenshot that I've included to the right. There is also a link on this page to the Google Maps Local Business Center where you can add coupons to your business listing for free. Check it out here..