Welcome back!!!
Errrm - crash course - surely I will leave a lot of stuff out, but here goes -
MAME - Analog Plus gave us dual mice, and spawned NoNameMAME before the Mame core changed and broke both of them, but now MAME 0.105 will have dual mice in the main build.
Frontends - MAMEwah has pretty much dominated the scene here, but you could also check out MALA for cocktail cabinets (especially) or AtomicFE.
Howard Casto introduced Johnny5 which allows you to show your control panel and what buttons are required when you pause MAME.
Hardware - As others have said, you really need to check out
www.groovygamegear.com and RandyT.
Remember 1Up's Spincade - Not sure if that is new since you left or not - now a cool commercial project at
http://www.spincade.com/, although I still somehow preferred the original at
http://www.robandmitsue.com/1uparcade/Blinky Lights - Knievel really started this trend with his Neon-MAME - See
http://www.knievelkustoms.com/cabinetcontrols.htm and the links back to BYOAC. Also see his Flyercade. Shawn gave us translucent microswitch buttons. RandyT came up with Electric-Ice lighted buttons. Ponyboy has leaf-switch modules that fit microswitch button holders. RandyT has the RGB-Drive snap-in modules for microswitch buttons. Whammoed (I think) has the lighting modules for true leaf-switch buttons. RandyT has the LED-Wiz controller and MikeQ is working on PowerMAME which allows you to make things blink from inside MAME. Also, RandyT just introduced the Electric-Ice Lighted Trackball.
Encoders/Interfaces - The MK series of encoders came and went. Daveb and Ultimarc introduced encoders for analog controls (yokes and flightsticks and wheels and pedals). RandyT introduced both low-priced keyboard encoders and gamepad encoders, and the Opti-Wiz for trackballs and spinners.
Spinners - Oscar created a Tempest and Discs of Tron replacement spinner, than vanished from the scene as RL got the best of him. He also sold joystick restrictor plates and mouse hacks. However, RandyT now has the Turbo-Twist spinner and Slikstik has the Tornado spinner - and Whammoed is working on a spinner.
49-way Joysticks - DaveB and RandyT both had interfaces for these, but RandyT figured out how to make the GP-Wiz49 control the joysticks so it works as either a 2-way, 4-way, 8-way, or 49-way stick. (I'm not kidding!!!)
Switchable joysticks - Ultimarc introduced the J-Stick, Mag-Stick, E-Stick and Euro-Stick switchable (4-8 way joysticks) and made the Mag-Sticks switchable from above the panel. RandyT introduced the Omni-Stick and Prodigy joysticks, the latter is also switchable from above the panel.
Yokes - Menace made a cool BYOAC repro yoke.
www.gamecab.com made one or two commercial ones, but I don't think they made anymore.
Tron handles - Fozzy The Bear is making these (soon?). Tom at Specialty plastics made some and lots of people did conversions to attach a flightstick handle to a arcade joystick.
Joystick handles - Slikstik and RandyT both have cool replacement handles for arcade sticks.
Shameless plug - I have my own webpage at
www.mameworld.net/tigerheli detailing a lot of this . . .
HTH