First things first: Safety. This project will require you to use a power drill, cut difficult material with a sharp knife, and to solder electronic components with a hot soldering iron. If any of that scares you, you shouldn't do this project. Wear safety glasses when using powertools.
Next: You will need the following items to complete this project:
1) A 1 and 1/2 inch diameter "slip on" PVC endcap (from the plumbing section of your local hardware). This will form one half of the mic shell.
2) A 1 and 3/8 inch diameter metal fence post cap (From the garden section of you hardware store). This will form the second half of the mic shell.
3) A package of 1 and 1/2 inch diameter rubber "cups" (for putting under you kitchen table's legs)
4) A 10 to 100 K ohm log taper potentiometer (for the voloume control, you can get these at rat shack)
5) A 1/4 inch mono panel mount guitar jack (again, rat shack)
6) A microphone element of some kind (mine comes from an old AudioTechnica ATR30 microphone I got used at Savers for $3.99. New it will cost around $30. You can use any element you like for this project)
7) Some hookup wire, acid-free solder for electronics, and some electrical tape.
8) Optionally: some cotton balls, spray paint, an old dryer cloth or other piece of cloth, a knob for the volume control.
Watch the first half of this video to hear more detail about the PVC end cap and fence post cap: