Break-ups, flirting, come-ons, disrespect - the truth is you only need to learn a few acronyms to have a good instant messaging vocabulary.
I suggest looking at a few websites for a more official dictionary of language. For example, you may want to try:
*http://www.webopedia.com/quick_ref/textmessagea bbreviations.asp
*http://www.webopedia.com/quick_ref/ textmessageabbreviations.asp
Here's a small sampling of the ever-increasing amount of instant message lingo.
AIGHT - All right.
AYSOS - Are you stupid or something?
BF/GF - Boyfriend/Girlfriend
B4 - Before
BBL - Be Back Later
BRB - Be Right Back
CYA - See Ya.
F2F - Face to face.
GG - Good game
G2CU - Good to see you.
LTR - Obviously, "later". Simple goodbye.
LOL - Laugh out loud.
LMAO - Laughing my a* off.
MYOB - Mind your own business
n00b - newbie, or novice, slightly pejorative
OMG - Oh my goodness/ Oh my god
PLS - Please
ROFL - Rolling on floor laughing
RTFM - Read the f*ing manual
THX - Thanks
TTYL - Talk to you later
WTF - What the f*?
WB - Welcome back
WYSIWYG - What you see is what you get.
While not comprehensive, this small list should be enough to learn most phrases in instant messaging.