Mash-ups

Google, Yahoo and soon Microsoft are publishing documentation making it easier for programmers to link any Internet date to Web-based maps. Marrying Maps to Data for a new Web Service.

One of the next big growth areas on the web will be contextual advertisements tied to specific locations.  The ads would be embedded in the map you generate in a search inquiry.

Say you could view all the houses you were interested in a certain area, all on one map.  That's what Paul Rademacher created in housingmaps.com when he overlaid real estate listings from Craigslist onto Google maps

Mash  -ups they're called, hybrid web services, part of Web 2.0.

"Web 2.0," a new generation of Internet software technologies that will seamlessly plug together, much like Lego blocks, in new and unexpected ways.
"These are small pieces loosely joined," said Tim O'Reilly, chief executive of O'Reilly Media, a publishing and conference company based in Sebastopol, Calif. "People are creating new functionality by combining these different services."
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Yahoo is hoping that groups of Web users will emerge to overlay its maps with restaurant reviews and other kinds of contributions.
"This is not so much about creating a virtual world, but rather helping people with the real world," said Paul Levine, Yahoo's general manager for local services.