Grappos.com is an online store locator for wine. The site has a huge database of wines from wineries, distributors and retailers which means they are able to tell you which local store is stocking the wine that you want.
To search for a particular type of wine you just need to enter the name of the wine and your location and Grappos.com will show you all the stores selling that wine on a Google Map. You can even create a link to any search by executing a search and clicking on "Create Link". This service is already being used by wineries as a product locator on their own sites.
Grappos.com is also about to launch a blog that will feature user reviews. There is an iPhone application in the pipeline that should be available soon.