So, this is what you'll need to build your microscope:
1 x USB Webcam - I have used an xBox 360 camera from eBay
1 x 50mm diameter, plastic 'twist pack' or 'Bolt case' - if you know someone who works with machine tools they might have a spare. I've used a DP50 050, from Rose Plastics, but I had to buy in bulk.
3 x card or MDF discs - in my original designs I used 2mm mount board, which works fine. Templates are here.
1 x 5mm, bright white LED
1 x 220ohm resistor
20cm of thin wire (single or multicore)
1 x piece of thin, flexible card - I used an old cardboard tube
Double sided tape
Impact adhesive and/or glue gun
Tools that you will find handy include:
Hot glue gun
Soldering iron and solder
A scalpel and blades
Small phillips screwdriver