Pentium 200 & motherboard w/ onboard sound (Yamaha OPL) & video (ATI Rage)  ::  eBay $26
Due to the motherboard mounting directly under the monitor, I knew there wasn't going to be room for conventional video or sound cards.  My motherboard requirements were that it needed to be an ATX form factor and have onboard video & sound.  I lucked out an won an eBay auction for a board that met my requirements and it came with a CPU.   I have no idea what kind of board it is, as there are no markings on it at all.   The bios flash screen has a Sony logo on it, but there's no indication of the board manufacturer.  The onboard sound chip read "Yamaha YFM701", and I was able to find DOS drivers for it on Yamaha's website.  No problems running the onboard sound under MAME in pure DOS.  :)

Removable administration remote control  ::   Radio Shack ~$10
As I am using a keyboard hack for the interface, I needed access to the MAME configuration options, but I didn't want to clutter up the control panel with a bunch of otherwise useless buttons.  I have had many people use my other MAME cabs, and they always end up in the configuration menus somehow during gameplay.
There are other ways to lock people out of the config menus, but making a removable remote seemed like a really neat idea, so I figured "why not?".  The remote currently has the computer power switch, tab, and enter keys with room for about 3 more buttons.  The buttons and project enclosure were all purchased at Radio Shack.
Project Enclosure - Radio Shack #270-1804

External serial DB9 com port
The expansion port allows a connection to a mouse or the future trackball / spinner module(s).

14" Computer monitor  ::  $20
The monitor was picked up at the Michigan State University "Re-Sale Barn".   The university sells off all their old stuff once a week.  You can definitely find good bargain buys there.

Controls

8-way Wico leaf joystick  ::  videoconnect.com $10.95
I have the Happ Supers on my upright cabinet, and I think they are great.  For this project, I wanted to make the control panel as classic looking as possible.    The ball top Wico has the best classic look and feel, in my opinion.
Custom paint job on the stick.  A plastic primer coat, two base coats, and about 15 clear coats.

Competition pushbuttons  ::  Happ Controls $1.55 ea.
These were left over buttons from a previous project.  It was just luck that they matched my color scheme.  To be honest, I don't care for their feel for classic games.  I will be ordering the Horizontals with my next Happ order.

Mini-Buttons  ::  Radio Shack $1.69 ea.
I used the mini-buttons for the Player 1 start, Player 2 start, coin insert, and pause buttons.  The mini-buttons were chosen because of their small size, and to keep the control panel clean and un-cluttered.
Red buttons - Radio Shack #755-646
Black buttons - Radio Shack #755-644

Escape button
I had an extra mini button from a previous project years ago.  It is a similar to the control panel mini-buttons, but a slightly different style.  I placed it under the control panel on the right side to keep it from being accidentally hit during a game.

Lack of controls??
In an effort to keep the control panel as classic looking as possible, I chose a seemingly sparse layout.  With only 3 buttons and a single stick, the game compatibility is limited.  Seeing as I have an upright with all the controls I could want, this doesn't bother me at all.  There is an additional control module in the works now that will plug into the external com port.  I did choose Centipede side art, right?  When the trackball module is complete, I will add it here to the controls section.