To add to Aurel's post (most of this is the same as on his blog):

Supplies:

1) Multimeter ($30 at Radio Shack, a lot cheaper from ebay)
2) Wiring to connect the PSU to your hubs (can also just snip off the plug from one of the cheap 1A/2A power supplies and strip the 2 wires): http://www.mcmelectronics.com/product/27-5990
3) Extra Power strip
4) Philips Screwdriver
5) More common sense than me (I initially bought a 12v PSU and blew up 2 hubs...Yeah - a loud pop and smoke haha)

After getting a power strip and literally just snipping off the plug, you should have 3 wires, strip the insulation off each of them so you have inch or so of exposed/bare (copper?) wiring,  

You need enough stripped so you can fit all 3 wires on their respective screws but not too much so when you close the little plastic safety latch there is still enough exposed wire to still end up hitting the wire and shocking yourself.

Green wire connects to  GROUND (the weird symbol)
Black (may also be red) wire connects to L(ine)
White wire connects to N(eutral)

Keep it unplugged.

Get the plugs you ordered -
White wire is + POSITIVE
Black wire is - NEGATIVE

This is how I lined mine up:


+     +     +     -    -    -   So first hub i connected got the 1st positive with the 1st negative, second hub got the 2nd positive with the 2nd negative, etc...
|                   |
---------------

I had more than 3 hubs so i doubled up with +/- terminals.  I think I have 5 connected total.  

Make sure voltage switch is set to 110 if you're in the US. Plug in the PSU, it should power on.  Make sure you have a fan on it if it didn't come with one built in. Take the multimeter, touch the black probe to the first negative screw/terminal then touch the red probe to the first positive screw/terminal.   Adjust voltage as needed to make sure it reads 5 and 5.5v.  When you're done, plug in your hubs! And close the plastic safety hatch thing.

This is how I got setup running (40A) and it's been going strong for over a month.  If I have anything wrong here please let me know so I can change it.  Here is a close-up of my PSU: