The Astrolabe
Language Hat particularly tipped me off to the great astronomical links which have been appearing at plep. Thence comes this interesting site about the astrolabe. Good stuff, with a handy links page. They'll even sell you an astrolabe, computer generated for the coordinates and date that you request, and printed on card stock. The fifty page book it comes with is probably worh the US$25 all by itself.
We saw some beautiful astrolabes in the Musée des arts et metiers while in Paris, along with many other wonderful instruments and devices. I'll have to step up the pace of my Paris posts, because I've still got some fun stuff to share.