NEW YORK (Business 2.0) - Ever since Google opened up its database of map and satellite imagery a month ago, interactive maps have been spreading across the Web.

These are not stale and static MapQuest maps. These are quirky, creative, eye-opening, idiosyncratic maps that can be made by anyone with Internet access, a few programming skills, and a little bit of imagination.

There are Google (Research) maps of the recent London bombings, Chicago crime scenes, cell-phone towers, free Wi-Fi hotspots, weather conditions, real estate listings, New York City tourist spots, people looking for dates, homes of sex offenders, and even urinals.

Yahoo! (Research) has also opened up its map database, and people have created Yahoo! maps of table tennis tournaments, San Francisco dog parks, restaurant locations, sneaker shops, and the wineries from the movie Sideways.

The newest entrant, launched last Monday, is Microsoft's (Research) Virtual Earth. It offers impressive mapping and aerial photography. If you can imagine it, now you can map it.

And these maps are just the latest examples of how Google, Microsoft, and Yahoo! are opening up their massive technology platforms (through application programming interfaces, or APIs) for others to improve on, as long as no one uses their platforms to make money. Maps are so familiar and easy to understand that this will perhaps be the most powerful example yet of APIs.

By opening up their maps for others to add data like the locations of sneaker stores or sex offenders, Google and Yahoo! hope to tap into the culture of participation and community that powers the Web.

Online, consumers are active participants in creating the information they consume: blogging, podcasting, photo sharing, programming, and now mapmaking. It's a new way for people to express themselves.

What's fascinating about these maps is that they have the potential to link all Internet data to the physical world. Any data feed that includes a zip code or street address can be mapped.

Take real estate listings from Craigslist, add them to Google Maps, and you get HousingMaps. Combine Hot or Not personal ads and Google Maps, and you get a handy map of potential hot (or not) dates. Plug traffic-cam video feeds into Yahoo! Maps, and you can check out how traffic is .

Map murders in Chicago, burglaries in San Francisco, or breaking news by dateline. There are even sites where you can bookmark the world with information about each spot you've visited. The number of potential maps, just like the number of potential blogs, is limited only by the imagination and willingness of the people who create them.

Google, Microsoft, and Yahoo! couldn't possibly come up with all of these map applications by themselves. And why would they want to? It's much better to outsource all the work to your customers. The underlying map technology that becomes the most popular will eventually strengthen the platform of the company that provides it.

The Web is the new operating system. And, in software, the more people who build on top of your platform, the more influential and indispensable your technology becomes.

Once you've established dominance, you can figure out how to use your platform to make money. If local ads become the next large growth market in search, wouldn't maps be a great place to show them? Google's AdSense places text ads on other Web sites; the same thing could be done with maps. The company could call it MapSense.

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