This bay display is a combination of three projects. A Thermal fan control circuit, a voltage display, and a DIY badgelight.
The thermal fan control is a simple L200 voltage regulator based thermistor controlled circuit. I got it from here. The voltage display/monitor shows the voltage level via some LEDs controlled by the LM3914 IC, which is a simple LED driver. Here's where i got it from (click me). I incorporated the LED display to the fan control circuit so I would have a visual representation on how fast the fan is running. The signal wire is connected the the output line of the L200 circuit, which is where the power of the fan is coming from.
The badge light is just a piece of scrap acrylic that I sanded down to form a bevel. I drilled a shallow hole at the back and stuck a LED on it, which is connected to my mobo's network activity header so it will light up when, um, activity.

Here're some progress pics:

Here you can see the guide lines I drew to align the stuff on the bay plate. I used a big sheet of sign maker's transfer tape to protext the aluminum finish, and to have something to write on. I have the badge (GT of course) and my beveled piece of plexi along with a blue lighted switch. I kinda modded the lighted switch with a real blue LED since the internal lamp that came with the switch somehow still made a yellow light (you can barely see a 3mm LED slapped in the switch face down).

To install the whole thing on the case, I used a 5.25" floppy bay adapter so it will be easy to install. I also used a scrap piece of plexi as a tray for the circuits. I bent the floppy drive screw hole pegs down so I can screw the plexi tray on it (see the drawings on the plexi? right).

Here's how it looked like drilled and cut. That big hole in the center is for the LED on the badge light. I tried on the slide switch cap to see if it would look better. I just decided not to use it since it's ugly, and it easily goes off. Oh, and red LEDs are ugly too.

Here's a shot of the whole thing. The fan controller and the voltage meter circuit are all in one pcb. It's actually two square ones that are bought together, where you can snap it to have two squares. I had the voltage regulator heatsinks stick out in the back so that they would be cooled along with the ambient air in the case. I have left some space there to fit another circuit, which was the serial port IR receiver.

A closer look. I have mostly everything connected with header connectors for easy removal. That floppy molex fits perfectly. As for fixing the Lian-Li bay plate on the drive mount, I bent the flaps a bit inside so it will slide in the drive mount and snap into place. I just cut an extra hole so the snapping bump would have it's own place on the mount. It won't budge unles you press the flaps towards the inside.

Only one working so far. The first (left) display controls my two front intake fans. The slide switches are a custom contol setting for the circuit. I inserted a toggle to the powering of fans. It toggles between thermal control and full blast. I also have a smaller slide switch to set the bar graph from dot to bar mode. But I have the switch inside since I decided not to put it on the bay plate.

Here's a shot in the dark.

I don't have pics of the serial IR receiver circuit but the receiver LED is now positioned on the lower left hand corner of the bay plate. I just drilled a hole big enough to expose as much of the LED bulb, then beveled it with a sanding bit to create a little angle to help make the LED bulb more exposed. And also, I ended up not using the lighted switch. I was planning on putting two at each side of the plate area to control my CCFL and other lights. But the LED bar graph's PCB kinda took a lot of space in the back. So I guess I would have to put the light switches on a 3.5" bay.