I have no idea how a slide rule works, but I'd like to learn. I mean that's wrong. I obviously have an idea, but I've never used one, and I think it'd be good to show students how they work.I learned how to use a slide rule in high school. I still have the slide rule I learned on, as well as another one I won in a math competition. When teaching Algebra 2, I show them to my students, then I have them make their own (very low-tech) slide rule.
I just posted a Make Your Own Slide Rule worksheet (including teachers' notes) which you may use with your students. The lesson serves two important purposes: helping them get a feel for log scales, and applying the laws of logs.
In any case, I wondered if I could model a slide rule on GSP or Cabri or something....There are excellent Java slide rules on the Web (I included a link to one in the teacher notes to the worksheet.) But if you do model one in Geometer's Sketchpad, please send me the sketch, and I'll post it alongside this worksheet.