USGS Earthquake Hazards Program-FAQ - Seismographs

This site has information on seismometers, seismographs, and seismoscopes (the first of which, it says, "was invented by the Chinese philosopher Chang Heng in A.D. 132").

It claims that "It is relatively easy to acquire the necessary materials and build your own seismometer," and provides relevant links.

Since I know people who like to build their own scientific equipment, such as telescopes (including trying to grind their own lenses), I thought I'd throw this out there.

Have fun, guys. And let me know how it works out.