Big Brother Abbreviations & Terms:

AC America's  Choice
A contest  where the viewers select the winner.
ADLs Activities of Daily Living
(The stuff we all do, brushing teeth, housework, etc.)
BB Big Brother
(or producers that oversee or direct the houseguests )
BBH Big Brother House
BBT Big Brother Time  We post updates in Big Brother Time, which is Pacific time.
Brenchel The duo of Brendon and Rachel
BY Back Yard
DOR Drop Out  Request  A DR form HGs complete to quit the game.
DR Diary Room where they go to talk to Big Brother
FBB Fantasy Big Brother on the CBS Web Site
FotH Front of the House.   When we don't get to see something live,  they showed the "Front of the House"  in BB6, they showed the " Fish of the House" and  in BB7,  it was a fireplace and we called it  "Fire of the House." 
HGs The House Guests (players)
HoH Head of House
HT Hot Tub 
LD Lockdown: Confined either inside or out while BB prepares or changes the set.
LR Living Room
PoV Power of Veto. 
The ability to remove someone from the eviction block.
RUTT Repetitive Unsportsmanlike Trash  Talk 
The constant and mindless verbal bashing of the other alliance.
VC Veto Challenge
WBRB We'll Be Right Back
WR3 The War Room 3 The secret HGs in the War Room, Scott, Allison, & Nate.

Chatroom & Email Abbreviations
Originally I didn't include these, I thought they were common, but I sure got a lot of questions about them.

AAMOF As A Matter Of Fact
AFAIK As Far As I Know
BRB Be Right Back
BBL Be  Back Later
BTW By The Way
FAQ Frequently Asked Questions
GMTA Great Minds Think Alike
HTH Hope This Helps
IMHO In My Humble Opinion
ITA I Totally Agree
IRL In Real Life, i.e. off the 'net
JSYK Just So You Know
L8R Later
LOL Laughing Out Loud
LMAO Laughing My Ass Off
OMG Oh My Gawd
OTOH On The Other Hand
ROTFL Rolling On Floor Laughing
TIA Thanks In Advance
TMI Too Much Information
TPTB The Powers That Be
TTFN Ta Ta For Now
WB Welcome Back
WTF What the F'?
WDYT What Do You Think