listed on Amazon. Aunty Dot and Uncle Frank have won a trip around the world; the book is full of their letters home (real letters in real envelopes), maps of their travels, and photos of their souvenirs. "Well, here we are in busy Beijing. Elephants weren't such a good idea--if we'd stuck with them we would never have gotten here! Beijing is a real contrast from our journey across the Tibetan Plateau, where we hardly met a soul. There were plenty of yaks, though--very useful animals!"
on Amazon); the CD-Rom runs fine on our computer but the website is gone. Crayons found this a lot of fun and fairly challenging, although she bought up all the "souvenirs" so fast, by playing a couple of favourite games and winning a certain number of points, that she lost some of her interest in trying out the other activities...we'll probably bring it out again next fall anyway.
another edition available on Amazon, but this one is pretty up to date (2006). Ponytails has been using this for general map skills, and the Apprentice also found it useful for a twelfth-grade class that required knowing facts about the "world's longest rivers" etc. It also offers little tips like the fact that if you point at the North Star with one hand and at the horizon with the other, the resulting angle will tell you how many degrees north or south of the equator you are. (How you're supposed to measure the angle while holding your arms like that, I'm not sure, but anyway...)
[2013 Update: There were a couple of other resources originally included in this post, but they turned out not to really make the grade, so I've cut them out.]