This is a redesigned Huxley inspired by the Prusa simplified Mendel.
http://www.thingiverse.com/thing:4148

It uses the PLA Bushings like
http://www.thingiverse.com/thing:4434
I modified the scad script to use 6mm rods.
(basically just put in 6mm for rod size and 12mm for width)

I have also redesigned the X and Y motor brackets to be able to use nema 14 or 17 motors. The Z now takes 2 nema 14 motors.

I designed it around 1/4" threaded rods and #6-32 bolts. It should work with 6mm rods and M6 bolts, but I'm not sure.

This should work with the same extruder as the regular Huxley. I believe.

The image is of the current build status, it needs the Y Stage and some belts on it before it will go, and an extruder. But the Z movement is working well so far.

Edit: Got the belts in and installed on the X Axis
Test Videos here
http://www.youtube.com/watch?v=rji863B-JnA
http://www.youtube.com/watch?v=pw6CKZPRubw

The design files are in SolidWorks

Edit 12-8-10: Found a problem with the X-axis parts.
the bolts used to tighten the rods in place had a nut bigger than the rod, so I put in a slot on the side. This weakened the structure to the point where tightening the bolts enough to keep tension on the belt, it would break the piece. I redesigned them after finding "Undersized Hex Nuts" (McMaster carr part 90760A007 for 6-32) which allow me to insert them the same as prusajr originally had. I also added more material to the sides to help with this. I am currently printing them out for testing.

Edit 12-9-10: I added more material to the x-axis parts to make them a bit stiffer again, I didnt get a chance to test the last version, so it may work just fine.

Print out a bunch of stuff and put it together how it makes sense :)
Found out somebody did a nice writeup for the fullsize one, which should be pretty similar to this one.
http://www.reprap.org/wiki/Prusa_Mendel#Assembly

BOM: This does not include and of the extruder parts
Printed Parts:
bar-clamp x8
belt-clamp x4
board-clamp x4
vertex x6
x-axis-carriage x1
x-axis-idler x1
x-axis-motor x1
y-bushing-holder x4
y-motor x1
z-top-motor x2

Motors:
X motor : Nema 14 or 17 x1
Y motor : Nema 14 or 17 x1
Z motors : Nema 14 x2
Enough bolts to attach the motors(M3 on mine)

Bolts:

6-32 1/2" bolts x22

6-32 nuts x22

1/4-20 nuts x A Bunch
1/4" washers x A Bunch
1/4" Fender Washers x 6

Bearings:
1/4" bearing x3
(I dont know the part number right now but they are 0.625" OD, which is like 16mm if your building in metric)

Edit: Current Bar sizes are as follows
Triangle frame threaded rod = 10" x6
Bottom across frame threaded rod = 8" x4
Top across frame threaded rod = 12" x2
Z bottom support threaded rod = 12" x1

Z Threaded movement rod = 8" x2

Z smooth rod = 9" x2
X & Y smooth rod = 11" x4

These are just because I got the smooth rod out of some old printers, and scaled the rest around them. All these dimensions should be able to be scaled up pretty easily. I should be able to get about a 6"x6"x4" printable area.

Kind of important
I attached the Z drive rods with some pieces of aluminum rod that I drilled through at 5mm and tapped halfway with 1/4-20. And then put a set screw in the side to hold it to the motor shaft. Im trying to make a printable version of this and still have it be as straight.

Here are instructions on how to put together the Z spring loaded antibacklash nut contraption
http://www.youtube.com/watch?v=k1xQw5gCoGE

You will need a nut that is drilled out just bigger than your rod, like this one
http://i.imgur.com/vUNVM.jpg