If you want to use an ATX power supply as a benchtop unit, without hacking it to pieces or risking fire and electrocution, then this approach is definitely for you.
NEWS: due to increasing inquiries I have made this item in to a complete kit. Let me know if you or your college / lab are interested. Full schematics BOM and assembly docs are provided too.
Step 1: Acquire the ATX PSU Benchtop Adapter PCB
This PCB has been specifically designed for this purpose, and is layed out for access to all the ATX supply votlage rails, even the standby supply and the "power good" signal. This PCB can be acquired from http://www.jordandsp.com/index.php?p=1_2_Projects. Since there was enough interest in using it, I had quite a few manufactured to get the price down.
Step 2: Get a Handful of Cheap Parts to Solder on to the PCB
I found the parts were easiest to get all of them from Jameco Electronics: www.jameco.com - but you could get them from Digi-Key, Newark or Mouser. I'm not sure who else stocks the Molex connector used for ATX motherboards, but Jameco have them at a low price.
You can see on the final step images the 4049 hex inverter, four resistors and several capacitors are on the front side of the board. On the back here you can see the binding posts just poke through their respective holes and you tighten up the nuts on the back, giving good electrical and mechanical connection.
The Molex-style connector (ATX header) is mounted on the BACK of the PCB. The new (black) version of the PCB is keyed with the connector so you can't install it the wrong way. PAY ATTENTION - There is in fact a silk-screen on the bottom of the PCB as a guide. Once you are ABSOLUTELY SURE you have it in the right position (as shown here), solder it in place from the FRONT SIDE of the PCB.
Before you solder any other parts on the board, you may wish to enhance the current-carrying capacity of the main voltage rails - you can do this by adding solder to them where there is an opening in the solder mask which you can see in this picture. This is optional - or course.
Step 3: Connect Your ATX Supply and Try It Out!
Simple as that! No drilling, metalwork, etc. and best of all you have access to ALL the supply's outputs.
The binding posts are also banana sockets as you can see here, so they fit in well with a breadboarding setup and other lab gear, like my Metex meter in the background :-)
Now optionally, you can mount this in a box using the four holes market MNT1 to MNT4, but the binding posts I used have a front panel mounting nut as well - visible in this photo - which stands away from the front of the PCB. Since there are ten of them, they will provide a very strong mounting mechanism (when I get around to mounting this in a box that is!).