heres a medium-resolution usb microsope i made for under $100 in parts (if you bought them new), had most of this around already and made a new tool :)
1 radioshack pocket scope
1 white led
1 logitech notebook pro quickcam (zeiss lens)
30 awg wire
heatshrink or black tape
hotglue gun (or whatever appropriate glue your prefer)
(cheap plug) http://www.makenyc.org/
Step 1: Modify the microscope
use your heatshink/tape here to insulate the leads.
test your light with a battery and make note of which lead is the anode/cathode.
on the camera board there is a small (freaking bright) orange led, *carefully* remove it, and wire the leads from our white LED in its place, with this camera the LED is under software control, usb provides all the power. make sure these leads have plenty of slack.
be generous with the hot glue to help act as strain relief on the wires; also be careful positioning the white led so that it points generally where the camera lens points