My entry: https://hackaday.io/project/159003-c61 -- a 6-bit pipelined CPU with schematic that fits on a single page.

A 6-bit Harvard homebrew CPU - excellent! Thanks for posting to the #One Page Computing Challenge 

Here's what I made today: https://hackaday.io/project/146481-szompu

Here's an image, with the extra register and little LEDs to tell you what data is being sent where.  (the register (OUTPUT_REG) is a fill-in for a co-processor, since the way that it communicate is through a shared register anyway)

someone please tell me how to embed images properly

See our #OPC-5 - a CPU for FPGA, in one page which is still evolving but has been seen to compute hundreds of digits of Pi. It's a 16-bit wide, word-addressed machine, with 16 registers.

What would be a good a demonstration that the one-page creation is indeed a computer? For me, controlling some hardware according to a program is ample demonstration, and for a more conventional machine, some kind of numeric processing, for example something like any one of these:

- print out the first N squares [1]

- the first N Fibonacci numbers

- the first N primes

- the first N square roots

- the first N digits of e

- the first N digits of pi

- Mastermind / cows and bulls game

- Higher/Lower guess a number game

- Lunar Lander game (not real time, of course! Turn-based.)

[1] Historically interesting: EDSAC ran a squares and differences program written by Wilkes. It had multiplication, so squaring was easy, but printing numbers in decimal always takes effort. http://www.cl.cam.ac.uk/~mr10/edsacposter.pdf

Running any kind of HLL interpreter would support any of those programs, but they could equally well be written in assembler. I'd be surprised to see a reasonable interpreter in one page.

Our #OPC-1 CPU for CPLD is a one-page cpu.

Okay, here is mine (but it is a rather long page): 

Ooh, a TTL machine - transport triggered - 8 bit - what's not to love?

Built in Front Panel, built and working.

AlanX

Here is the monitor program and the LED light chaser program:

Maybe you can join in over on the AnyCPU forum: see 

http://anycpu.org/forum/viewtopic.php?f=3&t=372

?

As you wish - the nice thing about this challenge is that you make your own constraints.

entries are in a PDF file with a single page ? :-)

(Actually that printout is from a web page - CSS can do green bar paper! With a background image for the holes. See http://www.pdp8.net/images/greenbar.shtml)