The Worldkit thread reminded me of this piece of software. Take any photo, input it into the software, and you get back a directory full of HTML files that allow you to view the image just like a Google Map. Basically, the same thing Worldkit does, but with Javascript and the actual Google Map API (meaning, you need a key to make it work) instead of Flash. Same result, different flavor. Variety is a good thing!

While I haven't used it on my own maps (I'm still very new to this), I *have* rendered one large one I scanned in... and it works pretty well.