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You can probably do this in the browser with WebGL: http://www.html5rocks.com/en/tutorials/webgl/webgl_fundamentals/ but it would require some programming, and a WebGL-compliant browser. But it should be fast since it would be using the GPU in most cases.
While very limited in their presentation, Google Fusion tables have the advantage that they present a very familiar map interface if you have a broad, non-GIS user community. After all, everybody has used Google maps.
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