Google Maps now sort of display Picasa web album photos in context. It's an option in the "My Maps" "Featured Content" collection.
I tried this in Old Montreal. I'd taken some photos there that display correctly in Google Earth (Lachine Canal bike/skate trail). I got mixed results. The images took a long time to appear, and I seemed to get quite different sets at different resolutions. I suspect they're still working on this, but I'm going to test it further today during a family skating outing on the Lake Wobegon trail.
It would be nice if it works, a way to build cheap "guides" for eccentric families like ours.
Update 8/31/07: It's still not working. My Lake Wobegon images haven't appeared yet, though I do see a few other people's images. The Lachine canal images I saw on Google Earth aren't in Google Maps today. Display of the images that are found is quite slow. I don't think the current model is going to scale, Google will have rethink this.