After reading the article John linked to I went to a local thrift
store and scored a Canon SD300 in fine working condition for three
dollars. I then found an article about how to mod the Canon SD400
which appears to be mechanically identical to the SD300. So I ordered
a couple batteries, a charger, and an 8 gig SD card. When the stuff
arrives I will be ready for it with a modded camera. I will at first
use an IR filter made from a floppy disc. If that gives me decent
pictures I will order some filters. One web site I went to explained
how modding the camera to be full spectrum and using filters external
to the camera instead of putting the IR filter in the camera not only
allows taking pictures in narrow wavelengths it also allows taking
pictures using only a couple ranges of wavelengths. This way you can,
for example, take pictures that show blue skies while at the same time
trees and grass appear stark white. When I get some good pictures I'll
post 'em to the Dropbox.
Eric