LE - Leading edge... (of the wing/tail/rudder)
TE - Trailing edge
CG or COG - Center of gravity (balance point)
AOA - Angle of attack (attitude of the airplane in respect to the pitch orientation)
WOT - Wide open throttle
High Alpha - High angle of attack
3D - Maneuvers performed at or below stall speed
DR - Dual rates on your radio
EXP - Exponential on your radio (computer radios)
EPA - End point adjustments on your radio (computer radios)
TR - Torque rolling
KE - Knife edge

These and all the ones others have listed above are generally what you'll see commonly used online as well as some of these in general conversation...

LOL - Lots of laughs / Laughing out loud
ROFL - Rolling on floor laughing
J/K - Just kidding
Noob or Newb or Newbie - Somebody new to the hobby or inexperienced in the topic of discussion

Brian