I've been playing with google images server and geotiddlywiki today with some interesting results.

I was thinking along the lines of - if GeoTiddlyWiki uses the same projection as Google Maps then using canvas's drawImage function you could put the static image in the background thus providing all the details Google Maps enriches for you (eg. city names,roads,terrain etc..) and still have the benefits of the coloured map painted on top of it. Then as a result of this you could save these static maps locally (feasibly everytime you accessed them it could save them in the background) meaning you have a portable map you can share with friends and use without the internet. This would also work wonders when you are looking for geocaches in a specific place such as London where the street details become much more important. I envision you could zoom in on London, knowing that the maps you see in your TiddlyWiki are now stored offline, enter an rss feed of geocaches in the area, and then go offline and find them.

Today I got the projection function working to match Google Maps projections but it still requires work in that it's not quite a perfect fit and translating and zooming are also not perfect. Steps in the right direction though I think!