Shapelock is a plastic that is made moldable with only hot water and is perfect for all kinds of do-it-yourself projects.
Pinball is great. Futurama is great. Home-built projects are great. Combine all three and you get a really cool result!
This is a PIC microcontroller project I did some time ago which turns my computer’s hard drive LED into a more interesting 10 LED bargraph display.
Harry Porter built a functional computer out of relays — including memory, ALU, registers, and all.
These microcontroller boards have options for wireless ethernet, wired ethernet, USB, and other goodies for semi-reasonable prices (as far as embedding in projects).