Type in a city or zip code, and it finds all the yarn shops nearby. http://www.knitmap.com You can filter your search by proximity/distance, whether it's open now, has seating, wifi, etc.
It also works on my iPhone , where there's an option to click "near me." Perfect for travel!
The search delivers a list of stores along with ratings and comments. You can link to store websites and see them on a map. Everything about it feels just right. Kudos to the developers, who are spot on in both concept and execution.