Wikimapia offers some nifty mapping tools, along with open source map tags of the world. Fun stuff. For instance, I outline below much of the Arnold Arboretum, where I often walk the dog when I'm in Boston.
Here's another one, from further aloft, featuring Downeast Maine and Acadia. I went sea kayaking up there this summer, though not nearly as often or as long as I would have liked.