Acronyms, Abbreviations, Leet speak, ...

LOL - Laughing Out Loud; Lots of love
AFAIK - As Far As I Know
ROFL - Rolling on floor laughing
BTW - By the Way
AKA - Also Known As
C U - See you
OMG - Oh my God
Pwn - Own (Typo)
LMAO - Laughing my ass off
G2G - Going to go
BRB - Be right back
Pop - Popular, Pop
GB - Game Boy, Giga Byte
GBA - Game Boy Advance
GBC - Game Boy Color
NES - Nintendo Entertainment System
SNES - Super Nintendo Entertainment System
NDS - Nintendo Dual Screen
BFF - Best Friends Forever
BF - Boy Friend, Brute Force
FF - Fear Factory, FireFox, Final Fantasy, Fighting Force, Foo Fighters, hexadecimal value for decimal value 255
THC - The Hacker Club
KEKEKEKEKE - Korean for HAHAHAHAHA
JMP - Jump
RET - Return
FTP - File Transfer Protocol
HTML - Hyper Text Markup Language
PHP - Personal Home Page, this is debatable.
JS - JavaScript, JaSon
HTTP - Hyper Text Transfer Protocol
SK8 - Skate
H8 - Hate
GC - Game Cube
GTA - Grand Theft Auto
SMTP - Simple Mail Transfer Protocol
CSS - Cascade Sheet Style
P2P - Peer to Peer
BIT - Binary Digit
LD - Load
DL - Download
WIN - Windows
REGEX - Regular Expression
MMORPG - Massively Multiplayer Online Role Playing Game
RPG - Role Playing Game
BPS - Beats Per Second
PPC - Pay Per Click
FPS - Frames Per Second, First Person Shooter
RISC - Reduced Instruction Set Computer
ARM - Advanced RISC Machine
MOAR - More
W8 - Wait
M8 - Mate
RPM - Rotate Per Minute
KB - Kilo Byte
MB - Mega Byte
TB - Terra Byte
PB - Peta Byte
RAM - Random Access Memory
ROM - Read Only Memory
HDD - Hard Disk Drive
USB - Universal Serial Bus
CPU - Central Processing Unit
ALU - Arithmetic Logic Unit
S. O. S. - Save Our Souls
CD - Compact Disc
PS1 - Play Station 1
PC - Personal Computer
LASER - Light Amplification by Stimulated Emission of Radiation
P&P - Postage & Packaging
Bot - Short for Robot
ARP - Advance Routing Protocol
DSL - Damn Small Linux, Also type of internet connection
ISBN - International Standard Book Number
MD - Message Digest
Sup? - What's up?
A. D. - Anno Domini
P. S. - Post Scriptum
ETC - Et cettera (meaning: and so on, ...)
PDA - Personal Digital Assistant
THX, TNX, THNX, TX - Thanks
PSP - Play Station Portable
SP - Service Pack, Small Pack
PR - Public Relations
VGA - Video Graphics Array
DIV - Division
HREF - Hyperlink Reference
IMG - Image
SRC - Source
SC - Source Code
FB - Face Book
K - Okay, Key
KK, Okay OK
KKK - Klu Klux Klan
Croc - Short for crocodile
Gex - Gecko
USD - United States Dollar
GBP - Great British Pound
Phool - Fool
AVG - average
AV - Anti Virus
NASA - National Aeronautics and Space Administration
URL - Uniform Resource Locator
URI - Uniform Resource Identifier
BASIC - Beginner's All-purpose Symbolic Instruction Code
ASCII - American Standard Code for Information Interchange
FORTRAN - Formula TranslatioY2K - Year 2000
LED - Light-Emitting Diode
QRC or QR Code is short for Quick Response Code (it's 2D code)
TBH - To be honest
AFK - Away from keyboard
ASAP - As soon as possible
AMAP - As much as possible (I don't know is this even used)
SQL - Structured Query Language (sometimes read sequel)
DDL - Data Definition Language
DML - Data Manipulation Language
U2 - You too.
BR - Break
IP - Internet Protocol
CRT - Cathode Ray Tube
ATM - Automated Teller Machine
DLL - Dynamic Link Library
WAMP - Windows + Apache + MySQL + PHP
LAMP - Linux + Apache + MySQL + PHP
CGI - Computer Generated Imagery, Common Gateway Interface
IRL - In real life
DBMS - Data Base Management System
WTF - What The F**k; Wow That's Fantastic (joke)
FTW - For The Win
FYI - For Your Information
SMS - Short Message Service
SIM - Subscribers Identity Module
PIN - Personal Identification Number
WIP - Work in progress
GUI - Graphical User Interface
CLI - Command-Line Interface
IDE - Integrated Development Environment
RAT - Remote Administration Tool
UDP - User Datagram Protocol
TCP - Transmission Control Protocol
VS - Visual Sudio
VB - Visual Basic
PS - PhotoShop
VBA - Visual Boy Advance, Visual Basic for Applications
FAQ - Frequently Asked Questions
OTP - One Time Password
PL - Programming Language, PlayList
TTYL - Talk To You Later
VIP - Very Important Person
JIT - Just In Time
TTL - Time To Live
UX - User Experience
API - Application Programming Interface
OCR - Optical Character Recognition
ID - Identity
IIRC - If I remember correctly
RC - Remote Controller
TY - Thank you
OST - Original Sound Track
CMS - Content Management System
MATLAB - Matrix Laboratory
SHA - Secure Hashing Algorithm
REM - as in Remember, Rapid Eye Movement
UI - User Interface
UX - User Experience

There are so many more...when I recall more I'll add here when possible.

If you see any errors or mistakes or you just want to add something please contact me.