There are any common forum and camping abbreviations.  There are some to help you get started:

HTT = Hybrid Travel Trailer
PU or PUP = Pop Up
TT = Travel Trailer
5er = 5th Wheel Camper rig
TV = Tow Vehicle
WDH = Weight Distribution Hitch
BC = Brake Controller

N2U or N2Y = New TO You (or New TO US, again depending on context.)
PO = Previous Owner
OP = Original Post (or Original Poster, when talking about the person.)
DO = Dutch Oven
HWH = Hot Water Heater

CG = CampGround
NF = National Forestry Service
NP = National Park
SP = State Park
COE = Army Corp of Engineers
W/E = Water & Electric (hook ups)
SPUT = Stupid Pop Up Tricks

Often people are referred to as DH, DW, etc - Dear or Darling Husband - Dear Wife
The starting D has also referred to Dizzy, Dorky, Dumbfounded or Dimwitted depending on the content.  DW is not DishWasher and I don't recommend using it.  :rofl:
DW  = Wife
DH = Husband
DS = Son
DD = Daughter
DSS = Step-Son
DSD = Stepdaughter
DGS = Grand Son
DGD = Grand Daughter
DMIL = Mother In Law
DFIL = Father In Law
DSIL = Son In Law (or Sister In Law, depending on context.)
DDIL = Daughter in Law
DBIL = Brother In Law
DSO = Significant Other (for those who can't make a decision)

IIRC = If I Remember Correctly
IMHO = In My Honest Opinion or In My Humble Opinion
IMO = In My Opinion
LOL = Laughing Out Loud
ROFLMAO = Rolling on (the) Floor Laughing My Butt Off
ASAP = As Soon As Possible
BTW = By The Way
FWIW = For What it's Worth
OMG = Oh My Gosh
TY = thank you
YMMV = your mileage may vary/your experience be different

If I'm missing any common ones, please share them?