DIY Laptop
Brietech writes "Ever felt like building your own laptop from (almost literally) scratch? This is a microcontroller-based "laptop" built from the ground up from a handful of chips and other hardware found lying around. It runs a self-hosted development environment, allowing the user to write and edit programs in "Chris++" on the machine, and then compile and run them. The carpentry looks like it could use some work, but it's a neat project!"
an OS in 96 bytes of RAM? Bring it on!
There is an interesting overview of guides to make a do-it-yourself laptop at Repair4Laptop. If you don't want to build it completely from scratch you can consider to make it as a so-called barebone or white box laptop. Barebones are also featured in a separate section of the overview.
A $50 FPGA can be made to work as a 256 color VGA driver (or any size lcd controller you like), and you can easily get it to accept PS/2 input from a keyboard.
Then you pick your poison for processors, coprocessors, etc - as long as it fits on the FPGA.
You have lots of options.
Mod me down and I will become more powerful than you can possibly imagine!