Worth a look at the work Google Australia have done on their own Google-product-powered election site: mashed-up maps, YouTube videos, Google Earth layers, and all that. More detail in this posting on Google’s Aussie blog.
They’ve clearly gone to a lot of trouble with the map’s boundary definitions; and I like the way you can filter seats by party and marginality, although the usability could be better. Hint: select at least one party and marginality, and look for greyed-out / non-greyed out party logos. I’m also very impressed to see the official Aussie term for an extremely marginal seat: ‘tight as’.