Here's a few I had to look up in order to follow along at first. There's a good chance I'm getting some of this wrong...and Yes, I agree in advance, that it's pretty bad that I had to lookup OGR.
Magazines
OGR: O Gauge Railroading
Manufacturers
MTH: MTH Electric Trains (formerly Mike's Train House)
GGD: Golden Gate Depot
Clubs and Non-Profit Organizations
TCA: Train Collectors Association
LCCA: Lionel Collectors Club of America
TTOS: Toy Train Operating Society
NASG: National Association of S Gaugers
LOTS: Lionel Operating Train Society
NMRA: National Model Railroad Association
Systems for Digital Model Train Control
DCC: Digital Command Control (Open source standard developed by NMRA)
DCS: Digital Command System (developed by MTH Electric Trains)
Legacy: Legacy Control System (Lionel's current electronic control system)
TMCC: Trainmaster Command Control (Lionel's original command control system)