It seems that you cannot include Google Visualisation Charts into a blog post directly.
So, I tried to include the output of a googleVis function as a gadget, but also unsuccessful.
Although you can include gadgets into your site template, it doesn’t seem to work with blog posts. So, here is the trick which works for me: the iframe tag.
The following geo map is included as

<iframe width="450" height="40%" frameborder="0" src="http://dl.dropbox.com/u/7586336/blogger/AndrewGeoMap.html">
</iframe>

As you can see, the chart itself is actually displayed in a page hosted by Dropbox and only inserted into this post via the iframe-tag.

For those of you, who would like to replicate the plot of Hurricane Andrew, here is the R code:

library(googleVis)
AndrewGeoMap <- gvisGeoMap(Andrew, locationvar='LatLong', numvar='Speed_kt',
                          hovervar='Category',
                          options=list(width=600,height=300,
                          region='US', dataMode='Markers'))
plot(AndrewGeoMap)
print(AndrewGeoMap, file="~/Dropbox/Public/AndrewGeoMap.html")