In light of the rather successful outcome of my first SVG challenge (not called such at the time), I present another:
Challenge: craft an SVG with transform/viewbox/clipping settings to map WGS84 (that's latitude/longitude, as real numbers between -90.0/+90.0 and -180.0/+180.0 respectively) coordinates to the Mercator projection (used by Google Maps et al), making the image (conceptually) a client side WMS layer or map canvas object you can draw on via javascript using latitude/longitude coordinates, on top of (for instance) Google Maps.
The outcome of such a feat would be a boom in what you can (tractably) achieve, using only client side tools, in the geomapping department, or map mashups, in broader terms. Feel free to use the Google Maps API, if it helps in the number crunching department. (I have a feeling the linear algebra could and should be pulled off with just well engineered transform matrices, though.)