HOW TO - Build a $1 compound microscope
Ok, unless you have a bunch of thing about your place that will work for this it might cost a tiny bit more, but not much!
MAKE: Blog: HOW TO - Build a $1 compound microscope
If you can take it apart and make it sing a different tune, it should be here. Info about hacking, modding, bodging common objects into new things.
I got a Dreamcast at EB Games for $19.99 and I can't believe how much you can do from it. From developing you own games to playing vcds and divx movies and not to mention the ports like Quake, Doom series, and Quake Simpsons!! If you got a Dreamcast in the closet take it out and you might end up playing it as much as your PS2 and XBOX.