Links:
Here are some good sites to help you get started;
Arcade@Home - Without a doubt, the best cabinet/emulation site out there. This should be your first stop.
The Cabinet Web-Ring - This site makes finding other cabinet sites really easy! Check it out.
Happ Controls - The biggest arcade supplier in the US. These guys carry a huge assortment of items. I still drool every time I pick up their catalog.
The Official home of MAME - The emulator that started the craze, find out what's coming up and what's new in the world of MAME here.
Build Your Own Arcade Controls FAQ - A great sire for info on the how to's of building your control panel. Especially usefull if you're considering some type of custom set up. (Spinners, wheels, etc...)
Lance Taylor's Mame Machine - The site that showed me that a home made cabinet could look just as good as an actual used arcade cabinet. Lots of helpful information here.
WICO - The Source - A long time maker of Arcade Joysticks. I didn't use them because they were in the process of restructuring when I started the project. Probably the only guys who still sell "leaf" type joysticks.
Hagstrom Electronics - Makers of fine Keyboard Encoders - If you're going with a one joystick set up you may want to consider using only a keyboard encoder as it allows for better DOS operation.
Hanaho - Home of the Hot Rod Arcade Machine and Control Panel - Give it a look before you start, It may be cheaper to just buy a cabinet or control panel for your machine. NOW WITH LEGAL CAPCOM ROMS!!!!
Project Arcade - Homesite for John St.Clair's book from ExtremeTech. A GREAT guide on how to build an arcade cabinet. If you're considering building a cabinet from scratch, it makes a great general reference book.
Gamer's Lounge - This is the gaming forum I spend most of my time at, it's not only filled with lots of good information, but it has an excellent group of people who post there. It's the kind of place where you can escape the |_eet speakers of the world and still talk about video games.