If you're a developer who loves to build mashups - especially map mashups - then you have to check out the library provided by Mapstaction. (And if you're end user, wait until you see the demos!) Mapstraction is library that provides a common API for various mapping APIs already in existence. This allows developers to use the Mapstraction API to build a mashup that supports nine of the major mapping providers including Google Maps, Microsoft's Virtual Earth, Yahoo Maps, and more.
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